The iOS 5 beta 2 is available for download via iOS Dev Center for developers which is compatible for iPhone 4, 3GS, iPad 2, iPad 1, iPod Touch 4G, 3G, and Apple TV 2G.
In June at WWDC 2011 keynote Apple has announced iOS 5 which includes more than 200 new features and company has also rolled out iOS 5 beta 1 to developers on the same day, whereas the final release of iOS 5 is expected in this fall.
Now, if you are a registered Apple developer then head over to iOS Dev Center to grab out iOS 5 beta 2.
See also the previous iOS versions