Did someone mention RUNNING?
http://www.runnersworld.com has some beginers work-out plans. They also provide advice for common problems like which shoe to wear. Check with your doctor if you have any doubts about exercise. Try this link:
http://www.runnersworld.com/home/0,1300,2-60-63,00.html
If the link doesn't work, it's in the "getting Started" section (and it's a little slow.)
Work on getting in shape this spring and summer. It won't happen overnight. Seek a local basketball officials' association. They may have an inside scoop on some rec leagues and what you need to do for next season.