Thirty Ten theme by Arron Jorbin was one of the first publicly released Twenty Ten child themes. He’s also written a great tutorial on creating child themes and what he’s done to create Thirty Ten that’s updated frequently.
It features a small theme options area and 3 layouts and he’s included some custom headers as well.
Arrons site is a great place to start learning about Twenty Ten and Twenty ten child themes, his tutorials are unique, detailed and he explains things very well.
You can download Thirty Ten here.