Oh, I'm suffering from this mightily right now. Just made an appt with the best massage therapist -- you want someone who specializes in sports for this.
Here's my favorite stretch, I like to hold it for at least a minute on each side. In yoga, we use 'yin stretching' for tough fascial tissue like the IT bands, gentle stretches held for a long time. It's stretch #1 on this page:
http://tinyurl.com/397y8e
Feels great.
Here's a youtube video clip of a boring physio lecture on the topic (related to runners)
http://www.youtube.com/watch?v=sz73i3O01d8