Just a week after the first iPhone 2.1 beta seed, Apple has released another 2.1 firmware release to developers. The new version appears to include several bug fixes.
"This is the second beta of the iPhone SDK targeting iPhone OS 2.1, including bug fixes to iPhone OS as well as an early implementation of the Apple Push Notification Service API. This API is not yet integrated with a live push server."
Apple has not announced a timeframe for the 2.1 release, but the included "Push Notification Service" was promised by September.
Despite early hints of turn-by-turn GPS and Copy/Paste, further investigation indicates that these may not have been new findings in the 2.1 firmware (and had also existed in 2.0). References to a new iPod Touch model, however, suggests an iPod Touch hardware upgrade in the coming months.
Not all registered iPhone developers have access to the seeds. The first seed was only available to iPhone developers who had been accepted into the program prior to July 11th (~4000 individuals).