Hamstrings, Suboccipitals, and Running Speed
in it Carson points out that releasing the suboccipitals - muscles at the top of your neck, base of your skull - increases hip mobility more that addressing the hamstrings directly.
Colin has posted about it too on his blog and all this ties in with the ideas of Tom Myers on Anatomy trains that I have posted about before - all your muscles are connected.
Really useful stuff.
Looks like Carson Boddicker is another one to follow!