Having had this problem myself earlier in the year and getting so fed up with it and all the conflicting information that you can find on it, I bought an e-book on the subject. It turned out to be basically a systematic review of all the evidence that exists on ITBS, the causes and cures. Sadly the only two things that have actual proven clinical results are surgery and long term rest, and by long term it means at least 6 weeks of complete rest followed by a lengthy transition phase back into full training. The conclusion on all the other treatment methods was that they probably won't hurt and they might help, although no-one has produced anything concrete yet. Because of this I figured the best approach was to just try everything I possibly could - foam rolling, stretching, hip strengthening exercises etc, and stick to the routine, doing something every single day, and building my runs back up very slowly (starting at 1.5km and increasing by about 0.5km per week). It's been a long process but I think I'm pretty much over it now.

The most important thing with any injury though is to find out the cause of it and treat that cause rather than just treating the symptoms. For some people it's a weakness in a particular muscle, or a tightness, or a defect in gait etc. For me I'm pretty sure it was the motion control shoes that the running shop 'prescribed' me to correct my overpronation, but don't get me started on that.....