One of my colleagues Animesh has been working on creating an Annotation based wrapper over Cassandra and we have finally decided to open source it for it to be nurtured as a part of the bigger community.
kundera is hosted on code.google and can be reached here – http://code.google.com/p/kundera/
Here is how to get started with kundera in 5 minutes -http://anismiles.wordpress.com/2010/06/30/kundera-knight-in-the-shining-armor/
The logic behind kundera is quite simple - provide ORM like wrapper over the difficult-to-use Thrift APIs. Eventually all NoSQL databases would like to have similar APIs so that it is easy to use NoSQL databases.
The initial release includes a JPA LIKE annotation library. The roadmap is to subsequently change it a Cassandra specific JPA extension. The other important feature that would be added is index/search using Lucandra/Solandra.