For what? Engines: Picco, Novarossi, RB and Sirio (all Italian BTW, RB is made in France but it is an Italian design)
http://www.unlimitedengineering.com for the shit when it comes to T-maxx upgrades. Hardcore Racing is only worth buying when it comes to Ti skidplates. All the rest of their stuff is over-rated and over-priced.
The JR R-1 was arguably the best radio out a year ago. I'm sure there is a new model out from them, but the R-1 is still more capable than most anyone needs.
For servos look to JR or Futaba. Airtronics is OK. Hitec is cheap and you usually get what you pay for. I have had terrible luck with them and I didn't race with anyone that would even consider using them. Buy one good servo that is half again as expensive as a Hitec, or buy 3 Hitecs so you have one to use while the other two are in for warranty repair and hopefully one of them will be back from repair (they take their sweet time) before the 3rd one shits the bed.
If you want a great nitro on-road car (only consider one if your plan to race seriously and there is a track nearby) look at either the Kyosho Vone-RR or the MTX-3. I have one of each.
For a nitro buggy the Kyosho MP-7.5 (I don't think that the new one is out yet but I'm not sure) is the most recent version of the car that has won the last 6 world championships. The Mugen MBX-5 is really nice, too. If you are looking at one of these go in knowing that you are going to have to drop $1k to get in the door properly. You will need the car ($400+), the engine ($300), exhaust pipe ($50+) the radio ($300 though you can spend less but why use a marginal radio on a top-shelf car?) servos ($200+, don't skimp here. If they fail, you WILL do some serious damage to a very expensive car), starter box ($100), at least one rechargable receiver battery and a charger ($50), and fuel ($10 per quart and it will take around 1 gal to break the engine in). These buggies are really quick and durable as hell. You will need a pretty big place to run one safely.
Go with a T-maxx to start with. There are custom parts out the butt for them and you can start upgrading it as soon as you get the itch for something more.