Empty Canvas is a nice, minimalistic theme for WordPress. I’ve implemented it here, but haven’t had a chance to generate a child theme off it to fix some of the things I don’t like (such as how it handles links). Overall, though, a nice simple base to start from.
The theme is not available for download anymore…
If you’re looking at building your own child themes, i would suggest you go to Studiopress.com and check out Genesis – i’m just taking it through it’s paces on one of my websites and i’m quite impressed.