My favorite yoga pose is pigeon. One-legged king pigeon pose, to be exact, or Eka Pada Rajakapotasana in Sanskrit. Most people have a love-hate relationship with EPR. It starts out falling into the I-hate-this-pose category, but then as people allow their bodies to soften into it and stop resisting, the many benefits of pigeon move it rapidly into wow-this-is-amazing-why-don't-I-do-this-more-often. If I had to pick one yoga pose, this would be it. I tell my students just starting out with pigeon to watch tv while in it for 5 minutes each side. That's what I did when I was pregnant, and believe me, it opened up my hips!
I had a yoga teacher once that called the hips the "attic of the body"; there's all kinds of dusty old stuff in there that needs to be cleaned out. And it's both physical and emotional stuff. I attended a workshop last summer where we held pigeon for about 25 minutes on each side; you should have heard the crying going on in that room. You don't have to hold it for that long to get something out of it, but I definitely recommend 25-50 slow, deep breaths on each side. Here's a picture of me in bound pigeon. Get the how-to
here.