WWDC
This is the first time since 2000 that the company has allowed non-developers to try out its OS before the official launch.
Since the public release date is in the fall, people accepted into Apple's beta program should expect to be able to download the new software sometime this summer.
Of course, testing beta software means users should expect lots of bugs. Plus, all users must agree not to "blog, post screenshots, tweet or publicly post information about the pre-release Apple software."
Here's the link for the beta program.