Recently I read about hundredpushups.com from one of my favorite blog sites Lifehacker.com. This was an appealing challenge for me.
My initial pushup test resulted in 35 pushups. I thought that I might be able to get to the next level but at 35 I was feeling like I might hurt myself trying. So 35 pushups and my age group placed me in a Rank 4 which then defines the training path you follow to reach the 100 pushup goal.
I also anticipate this working well for me since I ride my bike every other day. So for now I have physical workout of some sort about every day.