What are the hand signs in summoning jutsu?

1. Dragon
2. Rat
3. Monkey
4. Horse
5. Tiger
6. Rooster
7. Ox
8. Rabbit
9. Ram (Sheep)
10. Bird
11. Dog
12. Pig

These are the 12 hand seals, which correspond to the Chinese years.

There are also some more special ones:

1. Hand Clap (usually found in powerful secret or forbidden jutsu, also with jutsu that has something to do with the soul).
2. Cross Fingers (found in Shadow Clone jutsu)
3. Weird Cross Fingers? (the handseal which is done on secret techniques, found in Orochimaru's Curse Mark jutsu or on Haku's Demon Ice Mirrors jutsu.