What Norphy said plus:
What level of performance or reliability are you looking for? Ease of management? Are you looking for simple access, or something more advanced, like multiple SSIDs (distinct wireless networks), enterprise level security, seamless switching between access points (using the network while on the move), automatic channel management, etc.
Some enterprise solutions include Ruckus Wireless, Motorola's Wireless lan offerings,
and Aruba Networks.
All three of those are "Controller-AP" systems, where you purchase an expensive controller and then add cheap APs as needed, and all configuration (and in some cases, traffic) is handled by the controller. If your rollout is large enough, these companies may be able to help you design the network and do a site survey, etc. Their knowledge is worth as much as the system itself in some cases, because if you don't get it right, you end up adding access points to eliminate dead spots, troubleshooting overloaded wireless in crowded areas, general network instability, etc.
An option to consider based on budget is Ubiquity's Unifi.
These have a software controller for configuration but the APs can run without the controller, once set up. The price on Unifis are very low, but they are not a true enterprise level product.