Browser Based Teamwork Game (Awesome)

Iplop

It's a series of mini-games wherein your teammate's available time for completion is based on your own performance.

http://team.forsvarsmakten.se/english/

It's much more fun than I expected.
Give it a try! ;D

Mezalyth

I've done this before. LAN parties wreck face so you can coordinate.

Also, you can perform your teammate's objectives sometimes.

Fast_Fire

Tried this before, was fun watching everyone else fail

Humans

Well, we got above average with like 3:49:65. Then I got a headache and I quit!

Fun stuff