The iOS 5 beta 3 build 9A5259f is pushed to Apple registered developers that works for iPhone 4, iPhone 3GS, iPod Touch 4G, iPod Touch 3G, iPad 2, iPad 1, and Apple TV.
Now, if you are a registered Apple developer then head over to iOS Dev Center to grab iOS 5 beta 3 and to sync you also need to have iTunes 10.5 beta 3 installed.
In June, at WWDC 2011 event Apple unveiled iOS 5 with 200+ new features and also released iOS 5 beta 1 to developers and by the end of June iOS 5 beta 2 was made available to developers whereas the final iOS 5 release is expected in Fall 2011, with the launch of extended version of iPhone.