Alofthobbies is my first place i go to for any electronics or parts for flite test planes. As said before, amazing service, cheapest shipping anywhere and crazy quick shipping in California. 9 out of the past 10 orders (no exaggeration) have got to my mailbox less than 24hrs after i ordered it. Small company so you can actually talk to the owner. Only certified repair shop in north america for Frsky and he is usually the guy at shows demonstrating frsky stuff.
Hobbyking i use for all my misc building supplies i cant get at aloft and most all my batteries.
FPV gear i usually check out getfpv and readymaderc, both great companies.
Heads up hobby is great for electronics as well but aloft is more local to me. I still check them regularly though as they have an amazing amount of prop/battery data for motors.
I used banggood a lot this year. The prices are pretty unbeatable and usually free shipping but the shipping times are really bad. I use them for getting bulk constructions parts ahead of time. Lots of hinges, extension cables, wiring, etc.