Apple has released iOS 5.1 beta 3 in the Dev Center with a build of 9B5141a. This comes nearly a month after beta 2 was seeded. Downloads are available here.
To install iOS 5.1 beta 2 you will need your UDID registered. We have lots of slots for UDID activations. Simply use the PayPal form below and we will let you know via e-mail when your UDID is activated, usually in a few minutes.