Garter Stitch is usually thought of as a stitch for beginners, but just because it's easy doesn't mean you have to knit plain old boring rectangles, or that they have to look plain and boring when you're done.
My Garter Stitch Armwarmers actually are just rectangles of Garter Stitch, but folding and seaming them automatically makes them look more interesting and involved, even though they're not really. (We'll get into how you actually go about seaming Garter Stitch tomorrow.)
Pair them with the Garter Stitch Headband, which is a rectangle with shaped ends and a buttonhole (!) for a coordinated look even a beginner can pull of.
These are extra fun because you can probably make both with just one skein of light weight yarn. I used the BFL I bought at the Arkansas Fiber Arts Extravaganza, which you can see in this video over at my crafty blog. I have a whole other hank of it; any ideas of what I should do with it?