Mine is very, very simple.

I don't know if it's effective, but I feel like I should at least be doing something other than riding.

After a ride, and after the stretching, I do a set of sit ups with my legs crossed in the air. I then do birddogs (helps the lower back, where I have problems).

I then do another set of sit ups with legs on the ground and just getting the shoulder blades off the ground. I then do another set of birddogs.