Although I'm just starting out as a video contributor, I have had some sales on SS and MotionElements, so they're my top2 for the time being.
FT, 123RF: 1 sale so far. (Evil agencies, but I don't think their video prices are bad)
Pond5: According to many contributors, Pond5 is the market leader but I haven't had sales there yet.
Revostock, ClipCanvas, Canstock: no sales whatsoever. I'll keep supporting them.
I don't upload to Istock and DT, as they have horrible prices/commissions.