Pushups?

I plan on getting fit this summer, and excellent contribution to this are the websites http://www.hundredpushups.com/, http://www.twohundredsitups.com/, http://www.onefiftydips.com/ etc... I'm sooo gonna be hardcore! YEAH. While I'm improving my strength I will also be improving my cardio-condition. I'll be trying to reach my previous, but not reached, goal of running 7.5 kilometres.