Hot off the presses from Jonathan Payne:
VSTabs is a new Visual Studio 2003 add-in that replaces the normal tab bar with a new look tab control that supports tab combining and middle click tab closing. So far it is only at the "technology preview" stage but it is starting to become useful and the source code is available if anyone would like to add new features.
I have also updated my VSFileFinder add-in (previously mentioned at http://blogs.msdn.com/powertoys/archive/2004/04/20/117196.aspx) to fix a few bugs and support far better keyboard UI.
Both the add-ins are at http://www.zero-one-zero.com/vs/.