Since my hip starting bothering me over the winter, I'm pretty religious about doing the hip flexor stretch Zen suggested. I also do pigeon in just about every yoga class I go to. If you have tight hips, it can be hard to do. I also find one of the harder poses to do correctly, but maybe that's because my hips are tight.

For cycling purposes, I have to religiously do hamstring and IT band stretches. I also do a stretch when my sciatic nerve starts causing me problems after a long ride.