Microsoft has just released build 5744 of Vista for Technical Beta testers on Microsoft Connect (you must be a registered tester). And here's Jim Allchin's post on Connect:

People asked for it, and here it is, Windows Vista RC2! We wanted you to be the first to get these bits; next week they'll be available to a broader set of customers via MSDN and TechNet.

All your great feedback has helped us focus on nothing but bug fixes over the past month since RC 1 - each and every day. There are thousands of quality improvements since Windows Vista RC1. You'll probably notice improvements in performance, application compatibility, as well as fit and finish work. We will continue improving quality until RTM. If you are an ISV, please use this build (certainly at least RC1 or later) to get certified. Visit www.innovateonvista.com for more information on logo certification.

You are integral to this creation and refinement process. We are just around the corner from RTM and shipping this great product to the world. This will be the last build made available prior to RTM, so please keep the feedback coming so we can hit the finish line. Thanks for your help in finishing the job!