I have tried many engines and many sites, but none that really has the versatility I would like.

I am a very creative and very poor traveler, and I'm studying in Europe but have to get home (Cali) and around the States as well. In Europe, I can get to any gateway for pennies and don't mind length or inconvenience. Basically, I would like to be able to specify a number of possible departure cities (not necessarily close together) and a number of possibile arrival cities and then see the best prices for a couple week spread. (an ex: MUC, or PAR, or DUB, or LON to SMF, or NYC, or LAX, or ORD; between 7/31 - 9/8 = ?$?)

A couple of sites do parts of this, but even the "and nearby airports" option and the "flexible dates" option rarely coincide. Am I just asking too much? What is the most powerful and versatile (free) search engine that you know of?