Almost without exception, I've done some very light lifting alongside my running. Even in college, I would hop off the treadmill and hit the major leg muscles, or a few arm exercises with barbells. I wasn't serious about it, but I included it. After knee surgery, I added yoga to my running, and I loved how strong my body became from this. I would leave yoga feeling relaxed and balanced and like I just got my ass handed to me. And it wasn't a month after I stopped going to yoga that I got hurt - coincidence?
Right now, as I'm fighting this IT injury, I think I'm probably stronger than I've ever been. I've been doing probably 90 minutes a day - at least - of lifting, core work, stretching, and other exercises that just use the weight of my own body (squats, for example). I've never had this much cross-training before. And I've only been doing it for a month, but I can already see and feel the positive differences in my body. I can make my quads "pop" out of my legs, which is hilarious!!! I've lost around 5lbs (maybe more - I'm scared to weight myself after last night's homemade pizza/baked brownie incident). The few times I've run, I can tell that my hips are stronger and looser, and my pace has been significantly faster with less effort. The creaky feeling that I would have in my knees after even 2 miles has completely disappeared. It's also gotten me to do a lot more work on my recovering shoulder than I maybe would have, whining and complaining from the couch about my knee, and I'm hoping it's going to put me back in the pool that much sooner.
Over the winter, I was probably doing some light lifting about once a week, and I can see now that wasn't enough. This somehow makes this injury a blessing. I've found a way to be thankful. Without fighting the IT band problems, I would never have added this to my routine. Once I'm running more, I will probably back down from the 6-7x a week that it is now, but I will definitely keep it as an important part of my training. I've had a tendency to be injured a lot, and I'm hoping that with a more balanced approach to running, I will be able to stay on my feet (and off the couch).
Many, many people have been very generous with their advice as far as hip/core work and other IT-related exercises, and I'm always looking for more! Post your favorites in the comments!