I just finished these yesterday. I used a basic ribbed knit pattern but changed it so much that it is most likely my own now. The pattern is:
http://www.ravelry.com/patterns/library/best-friend-mitts
You can see my project notes here:
http://www.ravelry.com/projects/Bambi-M/best-friend-mitts
@Jan: I taught myself an afterthought thumb instead of using the gusset and was able to make the thumb spiral rib, too.
Now, can I remember how to post and resize a pic??