Sorry I can't help with an exact pattern, but I've made a few of these on my own.
To make a ballerina, you could use any pattern but elongate the torso. Then if you wanted to add long legs and arms that would help make it really cute. You could then crochet a little wrap skirt for around the waist and tie it on.
The main identifier of Amigurumi is the oversized head.
Here is one pattern. I can't see the pics at work, but from the description is could be what you are looking for.
http://www.ravelry.com/patterns/libr...mi-flower-girl
You could use this as a base pattern and adapt it as you need.