One rumor that has been going around for a while is a cloud-based music service by Google. It's being reported that we may hear something about that during the keynote this morning. To add more truth to that, the Music Beta by Google page just went live a few minutes ago and is currently accepting invite requests. You can't pull up the "about" page yet, but we expect it'll be up shortly (say within the next 2 hours).
Head on over to Music Beta if you're interested in the service.
Update: There appears to be a Music App in the Market now. We don't have any info on what the service will entail, but you can go grab it from the links after the break.
Source: Music Beta by Google