You meet people in real life all the time, but sometimes keeping track of them online is a tricky operation. Hashable is trying to solve this problem with a social stream of your real world connections.
The primary feature of Hashable is the ability to tweet an introduction between two people.
Once you've connected two people, you earn points and reputation.
When you intro two people, Hashable sets up a "Ice Breaker" page for the two parties to visit and see a few quick facts about each other, including followers in common.
Since you connect to Hashable with Twitter's API, you can track any interactions with people you have on Twitter. Even Foursquare checkins work too.
I think this is a pretty cool site, and whenever I want to introduce two people, I'll definitely use this. Every intro should be a quick as a tweet. Anything longer will lose someone's attention.