Apple has just seeded iOS 5.1 beta 3 to developers. If you're looking to get in the latest iOS beta and have a developers account, you can grab it via over-the-air (OTA) update or download from the developer site now.
The changelog hasn't fully been posted as of yet, so we're left wondering what all has changed but if you happen to spot anything -- by all means drop us a note in the comments and we'll update once we know some more.
Source: Apple
