Whatever you can choke down to keep your energy up.
With my son, my midwife kept telling me I had to eat something (it was a VERY long labor), and I just sooooooo did not want anything. I think I ended up drinking chicken broth and having those cheese peanut butter crackers... and that was hard for me.
After he was born, they made me a big plate of scrambled eggs, and those were the best scrambled eggs in the history of earth, I swear!
(not because they were anything special, but because I just hadn't really eaten in SO LONG)
These sound lovely...http://www.preciouspassage.com/laborade.htm