Click here for Lifehacker's instructions on how to add temporary color to your walls using fabric - you can either "wallpaper" a wall (or an entire room) or just add a few decorative accents.
All you need: fabric, starch, and a sponge or roller. And a razor knife (or sharp scissors) if you're planning on cutting out accent pieces. That's it!
Such a cool idea, and so perfect for renters.
Thanks to Alana for the link!