Lunchclub - Curated 1:1 professional connections
Coworker Coffee - Coffee with a different coworker each week
Serendipity - Serendipity is a PHP-powered weblog engine which gives the user an easy way to maintain a blog.
Lunch Roulette - Collaboration by grouping coworkers randomly for lunch.
Twine - Twine is an open-source tool for telling interactive, nonlinear stories.
Founders Cafe - Co-work with Founders from Stanford, YC, Harvard