Interested in nosql db.
Here is one among that
Redis is an open source, advanced key-value store. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets and sorted sets.
Used By web giants
Facebook, digg, flickr, twitter, stackoverflow and many more
To Read More: Check this out http://simonwillison.net/static/2010/redis-tutorial/
And for Interactive tutorial:http://try.redis-db.com/