I was actually thinking of combining this with tonight's game idea, but then I decided that these ideas to have fun, do something, and get writing could be put under just writing prompt anyways.
Act it Out
Just as the title says. Grab some friends and some costumes and act out scenes from your story or a book. And you never know, your friends could give you some ideas or make the story go in ways that you could never have thought of. And just to make sure, tell them that they're free to make the story go in anyways they see fit if they think it'd be better. Or not, its your story.
Read it out loud!
Another idea involves reading your story out loud, but instead, record it! If you have a recent computer and some form of a microphone look for a program that will record things. Some computers actually have a recording program built into it, but if not, I'm sure you can find a program for free. And once you've recorded it, put it on your ipod or other listening device so you can listen to your story whenever you'd like. Also grab some friends to read other character's parts or put some music in the background.