I stretch after a training ride (and/or in the middle, during refueling stops).
I stretch between warmup and race and then after the race. Essential muscle groups for stretching, in order of importance: hamstrings, calves, quads, glutes, hip flexors, neck.
I use a tennis ball or racquetball to get at knots in my traps, rhomboids, etc (leaning against a wall) and to massage my arches. Supposedly, this works for the legs and glutes, but I find that laying on a tiny ball is too awkward so that I don't relax whatever I'm trying to massage. I will occasionally use a foam roller on the IT bands and glutes, but I'm kind of a weenie using that or something like The Stick.
During race season, I had the need to schedule regular massages (from every week or two to once a month). The above techniques weren't doing enough without deep tissue, MRT, and acupressure therapy to keep me functioning. It is easier to have someone else beating me up than using the rollers. I need to remember to get periodic massages in the off-season, particularly when it gets so cold outside that my post-ride stretching is pretty useless.
I hate yoga.