I try and run 2-4 miles three to four times per week on my treadmill.  I also have a recumbent bicycle and rowing machine that I occasionally use.  In the summer I ride bike.  I went on numerous 20+ mile rides this summer along with a 50 miler.  Hoping to work myself up to a 100 mile ride next summer.  My right knee (and ambition) keep me from running more than 10-12 miles per week.....especially outside.