Ad Hoc distribution
From IPhone Dev FAQ
(Redirected from How do I use Ad-Hoc distribution to allow beta testers to test my app before I submit to the app store)
Apple has very good step-by-step instructions on the ADC portal (log into http://developer.apple.com/ and then go into the Program Portal and follow the instructions there).
This is a process that lots of people have trouble with. Here's a very good overview of how this worked in the 2.x SDKs and should be very similar for 3.0:
http://www.24100.net/2009/02/iphone-sdk-mobile-provisioning-0xe800003a-0xe8000001/
