Apple has released iOS 6.1 beta 5 for iPhone, iPod touch, and iPad. This comes just a day before beta 4 was set to expire, and represents one of the longest gaps between beta releases in iOS' history. Furthermore, beta 5 still hasn't shown up over-the-air (OTA), so rather than the faster, more convenient delta-update-in-place, if you want beta 5 now, now, now, you'll have to download it from developer.apple.com and do a complete update via iTunes or Xcode.
As always, this beta is intended for registered developers so they can try out new application program interfaces (API) and make sure their apps are compatible before iOS 6.1 goes into general availability (GA), presumably sometime in the next couple of months.
(If anyone gets the OTA, let us know. It's spoiled us and made us lazy!)
Update: There's still no OTA, and this build has characteristics common to a gold master (GM) seed, including no expiration date. So whether this was a GM that Apple show stoppered for some reason and had to release simply to avoid the previous beta from expiring, or its something more, we'll have to wait and see.
Either way, if you want it, you'll have to get it via iTunes or Xcode.