Buying airsoft guns online is very important and if you don't but from the right places, you may end up regretting where you ordered from. These are listed in order of my favorite.
AirsoftGI - www.AirsoftGI.com
Airsoft Atlanta - www.AirsoftAtlanta.com
Evike - www.evike.com
Stores to NOT buy from:
Airsplat - Commonly bought from by beginners because of their low prices. While their prices may be low, they are notorious for absolutely screwing up your orders; sending you the wrong gun, broken gun, etc. Some of the horror stories I hear are just ridiculous. Suck it up and pay the extra few bucks from AirsoftGI.
HotSpot Airsoft - Much like Airsplat. Crappy service and mediocre guns.
Pyramid Air - Similar to the above two.
HobbyTron - No! Not a good store. Never buy from a store that is a hobby store. Only buy from airsoft specialty stores like the ones I listed. Again, cheap guns.