Continuing their two-week cycle, Apple has just released iPhone OS 4 beta 3 for developers. You can download it now via developer.apple.com.
What bug fixes and new features lurk within? We'll have to wait and see (and keep an eye on the comments below...)
UPDATE 1: Apple has (temporarily?) removed the beta download from their developer site. It's not clear if there's an issue or not yet, but we're keeping our eyes open and will update again when (we're assuming not if) it returns.
UPDATE 2: The beta is back up. Go get it. Again.