The Visual Studio Industry Partner (VSIP) team at Microsoft has recently published pages highlighting partners with Visual Studio Add-Ons / Extensions in the following "Solution Areas:
Find solutions that help organizations capture and refine application requirements, and then manage them throughout the application development life cycle.
Secure Application Development
Find solutions that work in conjunction with Visual Studio and Visual Studio Team System to help identify and resolve security vulnerabilities, and enact secure development practices across the software development life cycle.
If your team builds applications for Java, Linux, UNIX or Mac OS, you can find partner solutions that work with Visual Studio and Visual Studio Team System that support cross-platform software development.
Visit http://msdn2.microsoft.com/en-us/vstudio/products/cc243534.aspx for links to all these pages and links to future "Solution Areas"