Here is an idea for applying Self-Control Therapy to Social Anxiety. This has worked well for me in the past and modified from Bandura's original work.
1. Chart the amount of time you spend in social situations. The act of charting alone will make you more likely to go out.
2. Plan your environment: Cut off your Internet access except from a school or library. This will force you to go out more. Can do the same thing with TV as many colleges, pubs, and some coffee shops have a television.
3. Draw a contract with yourself and state what you will do to reward yourself if you succeed in going out X many times in the next week.
Very often I have found that I tend to want to "think my way out" of problems, however, sometimes the cognitions change only after the behavior has been modified. I certainly think this was me at some point,