After doing a few spheres and tubes in amigurumi, you'll probably want to try out some different shapes just for variety's sake. How about a heart? Knits and Stitches has a great easy-to-follow pattern. The heart is made just with single crochets so this project is great for beginners.
Fancy up your heart:
» Add a string to it to make a keychain or simple tree ornament
» Add sequins and beads. Look at this cute pair.