Apple has just released iOS 6.1 beta 2, build 10B51505c to developers. iOS 6.1 beta 2 is available for iPhone 5, iPhone 4S, iPhone 4, iPad 4, iPad 3, iPad 2, iPad mini, iPod touch 5 and iPod touch 4.
iOS 6.1 beta 2 comes a mere 11 days after the release of iOS 6.1 beta 1.
If you're already on the iOS 6.1 beta, you can upgrade on-device and over-the-air (OTA) by going to Settings > General > Software update. Otherwise you can, as always, download the beta from developer.apple.com