IE7 Beta2 preview is now available for download from http://www.microsoft.com/windows/ie/ie7/

This beta2 release is primarily for Devs and ITPros (application compatibility and website compat testing)

See the IE website for an IT Pro checklist http://www.microsoft.com/windows/ie/ie7/itprochecklist.mspx

The IE blog has more details http://blogs.msdn.com/ie/archive/2006/01/31/520812.aspx