Romanian Deadlift (RDL) for Hamstrings, Lower Back

Here's a video demonstration of the Romanian Deadlift (RDL).  This exercise is superior to the standard stiff-legged deadlift (which can potentially injure the lower back).

As he mentions, you'll slightly bend your knees, try to keep your chest pushed out, keep the weight close to your body, and emphasize feeling the stretch in your hamstrings.  Don't try to go too low--just feel the stretch in your hamstrings and come back up. 

Going too low  puts your lower back in an awkward position (which is the problem with stiff-legged deadlift) and doesn't really help train the hamstrings.