I don't stretch before or {immediately} after rides to and from work, I rely on starting slow and gradually warming up by riding at a moderate pace until the legs are loose. I, however, do focus on stretching 3 x's a week in the evenings (something I have to resume on a regular basis). I find that the various ham/glute/quad/calf stretches we did as warmups for soccer/football practice are a good start. I also include some yoga stretches for my back/neck. While I don't think this is ideal, my busy schedule doesn't allow for much more. I think it's moderately effective in keeping my legs healthy and loose enough to get through week after week of commuting.