We've been introducing Cassandra into our stack at Gowalla over the past year or so. We recently released the fruits of some of that work. Chronologic is a service for publishing and aggregating activity feeds in social applications. It exposes a REST/JSON API via Ruby and stores all the feeds, subscription info, and objects needed to render a feed in Cassandra.
Here's a slide deck explaining it in greater detail (if you're pretty familiar with Cassandra you can skip through the bits on how Chronologic models its data in Cassandra): http://speakerdeck.com/u/therealadam/p/chronologic-you-put-your-feeds-in-it And the sources on GitHub: https://github.com/gowalla/chronologic/ We're quickly evolving Chronologic as we're building it into our next iteration of Gowalla. Feel free to watch us build the sausage or participate if you're already building an activity feed service and tying our wagons together. Thanks to everyone working on Cassandra, it's been a fun project to use!
