Serendipity - Serendipity is a PHP-powered weblog engine which gives the user an easy way to maintain a blog.
CoffeeRun - Let everyone enter their order for coffee runs
Coworker Coffee - Coffee with a different coworker each week
QuizBreaker - A fun online quiz game for teams to get to know each other
Startup Quote - Awesome founders provide wisdom about making things
Lunch Roulette - Collaboration by grouping coworkers randomly for lunch.