
Sandwich Condiments
An excellent sandwich is about the main ingredients, right? Well, yes. And no. As excellent as your roast beef may be, as fresh as your tomatoes or creamy as your cheese, there's one additional element that can make or break a sandwich: the condiment. The right condiment can make a good sandwich great -- and take a sandwich beyond lunch to become a hit at any meal. It can add the right counterpoint of flavor, whether that flavor is salty, sweet, tangy or some combination thereof. So when you are considering your sandwich for today's lunch, really consider the condiment.
Recipes listed are for tradional sandwiches as well as ones that are more inventive.

Ketchup
Ketchup has long been used for Hamburgers and Meatloaf Sandwiches.
Although an abomination to some who say mustard is the only way to go, ketchup is my favorite on hot dogs along with some freshly chopped raw onion. On hamburgers, ketchup and either dill pickles or sweet relish gives them the perfect touch for me.
This page on Hamburger toppings and ideas, will give you some new ideas on what to put on your burgers besides ketchup. Think horseradish, green peppercorn mayonnaise, Thousand Island dressing, guacamole, mango chutney and Caesar dressing to name a few. Most of these toppings are listed below.

Mustard
Mustard, in all its varieties adds a sharp counterpoint to many sandwiches - think, ham and cheese, or corned beef and cheese sandwiches. And we can’t forget sausage sandwiches, including hot dogs, bratwurst and kielbasa sandwiches. It's low in calories and packed with flavor. And with so many varieties from stone-ground to honey mustard to flavored mustards, you're sure to find a mustard that's your sandwich favorite.
Try cranberry mustard on your post-Thanksgiving sandwich. Slather honey mustard on toasted wheat, and add ham, sliced apple, and Brie cheese.
This page contains several rcipes for making your own homemade mustard, if you are interested.
And here are some other sandwich toppings made with already prepared mustard. Changing out the type of mustard you use will yield other flavor profiles.
Sweet Hot Mustard (German)
*Mustard Sauce (made with sour cream)
Horseradish-Mustard Sauce
Honey Mustard Sauce (for sandwiches)
Honey Mustard Dressing
Liverwurst and Onion Sandwiches

Mayonnaise/Aioli
Mayonnaise provides a creamy balance for sandwiches. A BLT would not be a BLT without that creaminess that brings all the ingredients together. Aioli, mayonnaise's cousin, used by the French and other Europeans to dip French Fries in, brings a similar texture.
Mayonnaise and aioli are basically the same thing: an emulsion (fancy word!) of oil, vinegar and egg yolks. Aioli is just a more specific version, calling for olive oil, lemon juice as the "vinegar" and adding garlic as a flavor. When homemade, both are pretty darn good as they are, but take well to additional herbs, spices, and flavorings.
Flavored mayonnaises and aioli are limited only by your imagination. Think of mayonnaise or aioli flavored with Dijon mustard, honey, or both, green peppercorn mayonnaise, chipotle mayonnaise, pesto mayonnaise, or mayonnaise with Creole or other seasoning added. Adding sour cream to any of these can lighten the dressing.
Some international variations on a theme, but made with sour cream and yogurt:
Chipotle Crema - Mexican Crema is similar to American sour cream adding creaminess to sandwiches. This flavored crema works beautifully on Mexican style sandwiches or burgers. Chipotle Crema recipe
Tsatziki - a Greek condiment made with yogurt and cucumbers that compliments Greek inspired sandwiches and burgers. Here is a good recipe for Tsatziki. Tsatzki is the traditional condiment used on Greek Gyros.
Another Greek condiment is Tahini Dressing (tahini is ground sesame seeds similar to peanut butter), made from tahini, olive oil, lemon juice and some thyme or taragon. A famous example of a sandwich that uses Tahini Dressing as well as yogurt as a topping is Greek Souvlaki (Beef Kebabs in Pita). This combination also adds a fresh, creamy flavor to Greek inspired burger.

Tartar Sauce
Tartar Sauce is most often served as a condiment with seafood dishes such as fried fish, and works equally well on fish and seafood sandwiches. Popular sandwiches are Fried Fish Filet and Crab Cake Sandwiches. Top with lettuce, tomato and tartar sauce and serve on a buttered, toasted bun. Other great fish and seafood sandwiches are New England Clam Roll and Shrimp and Oyster Po' Boys.

Pickle Relish
If you love briny pickled foods, pickle relish is likely your friend on the sandwich. Although typically used with hamburgers, hot dogs and sausages, what's to say you can't add your favorite pickle based condiment to any sandwich?

Hummus
This Middle Eastern dip made from chickpeas and tahini (tahini is ground sesame seeds similar to peanut butter) packs a load of fiber and a mayo-like richness without the calories. It is a terrific condiment for both vegetarian and non-vegetarian sandwiches.
A smooth, garlicky hummus with some lemon tang and cumin spice can be terrific on a burger, for example. Try combining it with roast beef with roasted red peppers and onions. Or keep it traditional and use it in a pita pocket with fresh tomato and cucumbers.
Hummus recipe
Beef Kebabs in Pita (Souvlaki) - I use a tahini dressing on these. Tahini is an ingredient in hummus.
Greek Burger - I also use a tahini dressing on these.

Guacamole/Avocado Slices
The creamy deliciousness of guacamole isn't just for the burrito-loving crowd; it's an excellent substitute for mayonnaise on many sandwiches. Guacamole is excellent on a BLT, for example - the latest food trend for restaurant prepared BLTs - or paired with sliced turkey, smoked or otherwise, and Swiss cheese.
Ripe slices of avocado work equally well, adding creaminess and moisture to sandwiches. Just slice them thin.

Pesto
Pestos are not just for pastas, they are for sandwiches, too. Try a basil pesto or sun-dried tomato pesto on a caprese sandwich (mozzarela cheese, fresh tomato and fresh basil) for garden fresh flavor and balance. The olive-oil and pine-nut base offers plenty of monounsaturated fat, and the basil is loaded with antioxidants. Spread it on your grilled-chicken sandwich.
Pesto recipe
Sun-dried Tomato Pesto recipe

Balsamic Vinaigrette
Using balsamic vinaigrette on a sandwich adds moisture and depth of flavor you might not expect from a mere sandwich. Use it sparingly though because too much moisture can turn a delicious sandwich into a soggy mess! If using lettuce or similar vegetable, you could toss the vegetable in the vinaigrette to add flavor without a lot of moisture.

Ranch Dressing
Just but just about any salad dressing can add a tangy punch to a sandwich. Try it on a chicken cutlet wrap, especially good, or in a vegetarian pocket.

Caesar Dressing
A creamy dressing made with eggs and oil (or mayonnaise in place of these), garlic, anchovy, lemon juice and Parmesan cheese. This dressing works especially well with chicken. Very popular today at delis and other sandwich shops are Grilled Chicken Caesar Wraps, or try a Chicken Caesar Club Sandwich made with cooked sliced chicken, crisp bacon, arugula or other fresh green, and a drizzle of Caesar Dressing on ciabatta bread.
Smoked or regular turkey would pair well with Caesar dressing, as would beef or pork. Fresh roast beef smothered with mushrooms that have been sauteed in a little Worcestershire sauce, then added to a crusty roll with some Caesar Dressing sounds good right now.

Russian/Thousand Islands Dressing
Russian Dressing and Thousand Island Dressing are practically synonymous today, although originally Russian dressing was made with yogurt or sour cream, a tomato product, such as chili sauce, and caviar, with some pungency from horseradish. Pimentos, chives and/or other spices were usually added. It's thought to have originated in the 1880's-1900. The condiment was named when the ingredients typically included caviar, a food often thought of as Russian.
Thousand Island Dressing is usually mayonaise based, with ketchup, relish, pickles, onions or chopped hard boiled eggs (the islands) added. It's a variant of Russian dressing. Either dressing is used on the Reuben now but Russian was the original classic (c. 1920).
McDonalds boasts their own “secret” burger spread, which is simply a manipulation of Thousand Island. McDonald's Big Mac Sauce
Besides Reubens and hamburgers, Thousand Island Dressing works well with any sandwich that would be complemented by pickle relish and ketchup, such as hot dogs.
Russian Dressing recipe
Thousand Islands Dressing recipe
Roumalade Sauce - a mayonnaise-based sauce seasoned with horseradish, ketchup, garlic and Worcestershire sauce that goes well with shrimp and other seafood. An excellent alterntive to Cocktail Sauce when serving shrimp that would work well on sandwiches.

Tapenade
Tapenade, the paste made of chopped olives, capers and anchovies can really kick up the flavor a notch -- or two. Since this Provencal treat is typically spread on bread, taking it to the sandwich is a natural progression.

Jams, Jellies and Chutneys
Pairing sweet and savory is one of the easiest ways to give your everyday meals gourmet flavor without a lot of culinary effort. Bored with your daily sandwiches? Jams, jellies, and chutneys are delicious additions that will break your lunch and dinnertime sandwich monotony. Pepper jelly is both sweet and spicy.
Mortadella & Fig Focaccianini
Bacon & Marmalade Sandwich on Pumpernickel Toast
Cranberry Sauce - Thanksgiving Turkey Sandwich
Other Condiments to experiment with
Horseradish - tradional for Beef on Weck
Barbecue Sauce
Teriyaki
Salsa
Tabasco or Siracha Sauce (or Red Pepper Flakes)