Microsoft is finally letting everyone have the ability to get notified when new beta releases of their software have been made available. If you decide to sign up for Microsoft TechNet then you will get notified when Windows Vista Beta 2, Office 2007 Beta 2, and Exchange Server 12 Beta 2 are released. This may not offer you the chance to test it, but at least you can keep up with what is available to testers.
If you haven’t been keeping up on the current news then I will recap for you. The current build of Windows Vista is 5308.60 (if you didn’t hear they released another build just days after the February CTP). Microsoft also recently released a Technical Refresh of Office 2007 to fix compatibilities with Windows Vista. Along with the compatibility fix they also did a slight overhaul of the Office GUI.