I ran across this article ,Using Java to access MongoDB, Redis, CouchDB, Riak, Cassandra, on java.dzone.com and thought it was interesting. It looks like this guy is playing around with building his own persistence layer in an append-only logger style, kinda cool.
One of the nice things about the article is that he shows a very basic persistence example for 5 different NoSQL data stores. I haven't seen anyone show side-by-side examples like this before. Cassandra seems to be the most involved in setting up a connection and performing a quick append, though none of the examples look very difficult.
Good luck Carlo Scarioni!