Lunchclub - Curated 1:1 professional connections
ChitterChat - Speak to 1 new person every 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.
Out of the Blue - A roulette for your contacts
Founders Cafe - Co-work with Founders from Stanford, YC, Harvard