Does anyone here do any kind of cross training just for the sake of improving cycling? I'm sure there are tons of tri-guys and gals out there who of course practice multiple disciplines, but do any of you dyed in the wool cyclists do anything like running, swimming, or rowing to improve your riding? What have you found works best? What can you do without joining a gym or buying expensive at-home equipment?

My cross training is more for improving cycling by correcting imbalances and strengthening muscle groups that cycling does nothing for.
Strength training is my main cross training exercise. I run from time to time as well but that is more to get a workout in when I do not have enough time or the weather is crappy. Winter is a good time to run.

I like to go for a few hour hike in the mountains the day after a killer ride. I think it improves my endurance. I don't hike hard, just zone 1.