This list is updated as of FEB 2012
The libraries/namespaces supported by CLR integration in SQL Server are:
Unsupported libraries can still be called from your managed stored procedures, triggers, user-defined functions, user-defined types, and user-defined aggregates. The unsupported library must first be registered in the SQL Server database, using the CREATE ASSEMBLY statement, before it can be used in your code. Any unsupported library that is registered and run on the server should be reviewed and tested for security and reliability.