Actually GAD doesn't have specific things you're afraid of, just that you're anxiouis about "everything" in "general" :-) I had that. Panic Disorder would be having Panic Attacks and a Phobia would be fear of something specific.

Good phobia site: http://www.panphobia.com

Good General Anxiety info: http://psychcentral.com/disorders/sx24.htm

You could have both Panic Disorder and GAD both.