OK, so quite a few of you are now asking me via PM about how to get onto the JPK Froyo build, and as much as I like to help everyone I'm afraid I can't be everyones personal IT helpdesk on this issue.
If you're interested, and I'd suggest your should be based on my experience with JPK, then you need to head to this thread at XDA developers - it'll give you all the how to's, caveats, and cautions you need to know. EDIT: Ok, apparently it doesn't mention you should uninstall any lagfixes you may have running on your 2.1 firmware before the upgrade - definitely do that first! There are instructions for removing the Voodoo lagfix at the official site, and XDA has instructions for removing the other lagfixes in their various official threads.
Once you're up and running you'll be able to do cool stuff like this: