Scott Hanselman has a list of the ultimate VS.NET Add-ins. Of his list, I personally use the CodeSmith Explorer, CopySourceAsHtml, devMatrics, NUnitAddin, Reflector (although most of the time not as an add-in - not sure why though), WS Contract-First, and the VSCmdShell.

His list is pretty comprehensive, and provides links to each one. Go check it out.