Apple released the long awaited first beta of iOS 4.2 today, download it from the iOS Dev Center. Since it is subject to the usual, annoying, NDA we will have to wait until the proposed November release date before discussing the details anywhere other than the Apple developer forums. What is already in the public domain is that this release will unify the iPad and iPhone forks of iOS and bring multi-tasking and all the other iOS 4 goodies to the iPad.
Usual disclaimers on installing beta versions of Xcode and iOS apply. If you are tempted to install it straight onto your one and only iPad you may want to wait a bit and see what issues other people are experiencing.