If you can’t get out and ride at least you can do some crazy moto trials stunts…
http://www.carmotogames.com/play/exclusive/moto-trial-fest-5.html -The Moto Trial Fest series of games has some of the nicest controls and action as far as I’m concerned.
http://www.carmotogames.com/play/exclusive/real-trial.html - seems to be made by the same developer.
http://www.miniclip.com/games/tgmotocross-3/en/ - These are pretty fun nice, controls a ittle more moto and a little less trials.
http://www.carmotogames.com/play/exclusive/mototrial-usa.html and http://www.carmotogames.com/exclusive/mototrial-uk.html- the controls aren’t as nice but it’s still fun.
and of course the original trials bike game creators http://www.redlynx.com/arcade there are a bunch in the series but Mountain Heights, Construction Yard are my favorites.
download all the classics here: http://www.redlynx.com/games/pc/trials-legends
http://canvasrider.com - a line rider type game, not as flashy but there are tons of tracks, build your own tracks if you’re super bored.