Internet Explorer 7 Beta 2 Preview is intended to enable developers, Web developers and IT pros to begin to test the new browser for compatibility with their applications and Web sites.

Link:
http://www.microsoft.com/windows/ie/ie7/default.mspx

Check out these posts too:

  1. Internet Explorer 7 Beta 3
  2. Internet Explorer Beta 2 Preview High Resolution Screenshots
  3. Internet Explorer 7 'Tips and Tricks'
  4. FAQ for the IE7 Beta 2 Preview
  5. Blocking Delivery of Internet Explorer 7
  6. IE 7 Beta 2 available
  7. Windows Defender out of beta