Whilst most of the Windows Vista followers were patiently awaiting Bill Gates' Keynote at WinHEC 2006 (scheduled to occur in roughly less than 2 hours), ATI quietly released new versions of its Catalyst Beta Drivers & Control Panel for Windows Vista build 5381 today.
At this point, since nothing has been officially said regarding Windows Vista Beta 2's build number, it would be silly to speculate as to exactly what this means - but nevertheless, the drivers are there, and we encourage you to install then (at least until another build crops up).
An interesting thing to note is that the drivers' exe files are labeled with the "RC0" tag, symbolizing one of two things: Either these are Release Candidate 0 drivers for ATI; or these are drivers intended to be used on Windows Vista RC0 - which is, as we know it currently, the internal moniker for "Windows Vista Beta 2"
Download: x86 Drivers | x64 Drivers | x86 + x64 Drivers
News source: ATI Driver Download/Info Page