For the parts, it depends on how much spare cash you have... I'd fully reccommend the BotBitz 85A's (just drop that into Google) by way of Speed Controllers, they'll set you back about £110 at most for the pair, but I've heard nothing but praise for them, and they've served me well so far. Motors, Gimsons do some ready-to-mount ones as Dave said above, alternatively there's the drill motors that can be easily modified to be decent enough drive motors - TeamExpat on Youtube (the Tormenta 2 team) have some very informative videos on that, there's numerous others about on there too.

You can get wheels practically anywhere (look for castor wheels of about 100mm diameter) but as Dave says, Robochallenge are pretty good for those too, since they do ones with a threaded insert purposely for mounting onto drill motor shafts.

The more commonly used transmitters from what I've heard are Spektrum DX5s or similar from that range. The budget one above will also do too (I use that one, myself, but I'm looking to upgrade)

As for batteries, it depends on your drill motors, you'd be best going with either a 3000mAh 3s or 4s LiPo, or a 12v NiMh if you get 12v drill motors, step it up to bigger batteries if you get higher voltage ones obviously, but it's a decent enough starting point. You can find those from www.hobbyking.com as you can with plenty of parts these days, they're not bad price-wise but it seems to add up on postage...

Finally, some advice regards putting a flipper on - if you know what you're doing, then by all means go for it, but I'd suggest you stick to making a moving box for now until you get an understanding of how it all works, and then go for the flipper - it's easy to jump ahead of yourself and be a bit ambitious which is what I did/am doing, but it does all come along soon enough. If you really want a flipper though, perhaps you could design a lifting mechanism that incorporates a high torque motor and later adapt it into a flipper? Might be a good idea to create a test platform out of wood or something that you can bolt all your parts to to see if your system works, always a good way to get the ball rolling.