I agree with most of the recommendations above. In addition, I think that Hobby People has some of the best sales, especially for Magnum engines. They usually have a great deal going on at least one engine, and they also have some good deals on Airtronics radios.
www.hobbypeople.net
I have had great service from Tower, Horizon, Advantage, and Hobby People. And I am a big fan of Hobby City for LiPos, motors, and small servos, but I wouldn't expect great customer service if there were ever a problem.
Good luck.
Edit:
One more guy that I like to recommend is Tom's RC. I think he is a small vendor, but he has great pricing, especially if you are buying several items. He gives quantity discounts on most items, and had the best prices I could find (by far) on a recent purchase of four Hitec 625MG's.
http://shop.tomsrc.com/