Besides Tabs Studio there are other Visual Studio tabs add-ins, though none of it is in active development now:
- WndTabs by Oz Solomon. Supports Visual C++ 6. I was a happy WndTabs user myself until Visual Studio .NET came out. Source code is available.
- VSTabs by Jonathan Payne. Supports Visual Studio 2003. Very small feature set. Source code is available.
- EasyTabs by Sven Ritter. EasyTabs for Visual Studio 2005/2008 original announcement in German, English translation. Supports Visual Studio 2005/2008. Developed on the basis of WndTabs. Source code is not available, but download is free.