Sauces derived from Béchamel sauce

Mornay Sauce (cheese)

Florentine Sauce (hot pepper, worcestershire sauce, spinach and herbs)

Nantua  or Shrimp Sauce (crayfish or shrimp, butter and cream)

Oyster Sauce (oysters and worcestershire sauce)

Anchovy Sauce

Sauce Albert (horseradish, mustard and whipping cream)

Cream sauce (heavy cream)

Mustard Sauce

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.