Watch the Dealing with Stage Fright: Just Go For It online guitar lesson by Jeff Scheetz from Blues Jam Survival Guide
Stage fright can be a very real fear for some people. One thing that will help you is to realize you are among friends and people who are very forgiving. Jam nights are a GREAT place to get up on stage for the first time! Remember, if you really prepare then when you get up there it will all go smooth, so "over" practice the songs you are going to do until you have them down cold.