I only ride once a week so I go to the weight room twice a week. Both days, I run 2 miles in under 20 minutes, and then I do crunches. Then one day I do my leg exercises, the other day I do my arms.
For legs, I use a lot of the equipment to to various lifting and things, but if you don't have equipment, just grab something heaving in each hand (I do about 10 lb) and do lunges (stand with your feet together, then step out with one foot and lower your back knee to a 90 degree angle, then stand back up normally again).
For your arms, you can do curling and pull-ups. Also, bench pressing helps if you have the equipment and somebody to spot you.
Even after a few workout sessions, I noticed a HUGE difference the next time I rode! It really does help!
Every ride, good or bad, teaches you something new.