Sauces derived from Béchamel sauce
Mornay Sauce (cheese)
Florentine Sauce (hot pepper, worcestershire sauce, spinach and herbs)
Oyster Sauce (oysters and worcestershire sauce)
Sauce Albert (horseradish, mustard and whipping cream)
Cream sauce (heavy cream)
Soubise Sauce (finely diced onions that have been sweated in butter)
Cheddar cheese sauce (Cheddar cheese, dry mustard and Worcestershire sauce)
The common ingredient is the béchamel base or white sauce.
Feel free to list others.