I like Flight Aware, but that's the only one I've ever really used. They've got a nice map (you can even overlay over the sectional), plus histories for flight

I like Flight Aware, but that's the only one I've ever really used. They've got a nice map (you can even overlay over the sectional), plus histories for flight numbers, routes, similar routes and lots of other neat stuff. I will admit it seems a little more geared towards pilots than the masses but there is lots of information presented well.