I've really liked some websites like... Try googling 100 pushups, 50 pullups, and a 200 situps if that's also something you'd be interested in. They have those words in the URL. I'd link them but not sure if I'm allowed and I'm on my phone right now. I've personally used the push-ups and sit-ups ones for a little while some time ago and found them quite effective, I don't know about others though. I plan on trying the pull-ups one too when I can get a bar.