Hack This Site really rocks! It challenges you to think. Be resourceful and you'll find tips on how to go about the missions.
It's nine minutes to midnight and I'm sleepy. It was fun doing the first five basic missions in one sitting. I'd still give it a go if my eyes weren't trying to shut.
It was really fun! So what are you waiting for? Try it! If you can, go contribute or advertise!
Now this is an online "game" that I can actually and would really like to play.