Wahine used to have in her blog a set of hamstrings exercises that I really like and that kick your butt. I'd looked for them really fast, but couldn't find them.

Essentially you put your feet on a ball and lift your butt up 15 times. Then you pull the fit ball in. On the 15th you keep the ball in and lift your butt again.

Sometimes I do these one leg at a time. They will work your hamstrings.

Veronica