'Not Pron'
Don't worry, it's totally safe for work, there's no porn, I'm not sure why they called it that. But I am only on level five...
http://deathball.net/notpron/
I think there are some 70 levels and apparently they get really, really difficult, but not impossible. There are various hints around the internet you can find through Google. I think if you want to give any hints here please use the spoiler tags. Spoiler:
They look like this. Write (SPOILER) and (/SPOILER) at the beginning and end of your hint, replacing the ( and ) with [ and ]. Enjoy!