Some new Jams anyone?

[maju dragon]

hey guys. Im in my youth group worship band and after service. me and some of my friends usually have a sweet jam session. well, last night, we were getting ready to have one and the guitarist was like, "cmon man, groove it up." and i was trying to think of something to play, but just couldnt. I personally hate it when people put some sort of pressure on me to come up with something on the spot. So sense there are like, 5 people actually interested in us and watching our every move, i didnt come up with something intil the guitarist finally made something up real quick. It was real simple but it was groovey at the same time. and of course the drums and guitarist did there thing and soloed it up and what not. but anyway, i was quite frustrated that i could come up with something to jam.
so my question is, does anyone have suggestions of songs/jams i can learn so when the situation comes again, i'll be ready to play something good and fun. Im trying to learn some Primus right now. (the more simple stuff) because its sweet and could be fun for a jam.
Thanks for all your suggestions.