Other good variations and add-ins include diced roasted yellow or red pepper, toasted pine nuts, slivered black or green olives. For the arugula, you could substitute 1/2 cup basil leaves cut in rubbons. Another idea: In southern Italian fashion, mix a pinch or two of sugar into the tomato sauce and top the pasta with toasted fresh bread crumbs. Or, for the anchovies or tuna, substitute smoked Alaska salmon in canned or frozen (thawed) form; Taku is an excellent brand that does a mail-order business. And sometimes I add 1 tablespoon capers and substitute 1/4 cup finely chopped scallions for the garlic and freshly ground black pepper for the hot pepper flakes.