There's now free registration at the VSIP site to become a VSIP ("Visual Studio Industy Partner"), which is the program whereby you can write a low-level package that integrates more deeply into Visual Studio than is possible as an add-in (or macro).  The VSIP program is great for 3rd party companies that want to sell add-ons for Visual Studio.  But anyone can participate, including hobbyists who just want to play around or add that one special feature they think would be handy.  -Chris