Great question Leah. I think it is a better idea to do your running before yoga. There is no research to support the idea that stretching before a workout prevents injuries. However, it is important to stretch after your run to keep your muscles from tightening up. So it would be smart to do your yoga after your run. I do think you can do both your run and yoga in the same day unless you are completely exhausted from your run. I have two great videos for runners.
Hips and Hamstrings which is available as a digital download, DVD and on the membership site.