Apache Cassandra: Introductory Resources
Recently, a friend mentioned she was hopping into a project which made use of Cassandra. I'd used Cassandra in mid-2014 to store, on TTL, the results from a continously running batch of Hadoop analytics jobs.
Jumping in to Cassandra requires re-thinking your problem from an Object Relational paradigm to one which fits Cassandra well. Below are some resources I found helpful when evaluating Cassandra for my project, as well as learning best practices for implementation.
As a final note - #cassandra on irc.freenode.net is usually active, and can be a great resource.