Lunchclub - Curated 1:1 professional connections
Serendipity - Serendipity is a PHP-powered weblog engine which gives the user an easy way to maintain a blog.
Donut Slack Bot - Get matched with a new coffee buddy each week in Slack
Founders Cafe - Co-work with Founders from Stanford, YC, Harvard
Snack - Read all your favorite email subscriptions in one app
Lunch Roulette - Collaboration by grouping coworkers randomly for lunch.