Riak is another of the new generation of NoSQL databases, that promises large levels of performance and scalability on large, intensive systems. I have worked on several large-scale websites that have hit relational database performance bottlenecks over time, so I am interested in the NoSQL movement as an alternative to RDBMS but so far have found it inaccessible.
FLOSS Weekly interviewed some of the developers of Riak recently, and I found them to be engaging and articulate in explaining Riak and NoSQL in general. You can listen to the podcast here: FLOSS 129: Riak.
Riak has a lot of different clients, including PHP and Ruby, so my favourite languages are covered which encourages me to give it a try. It will be interesting over time to see which NoSQL databases become dominant, as of right now with alternatives like MongoDB, CouchDB, and Riak, there seems to be a lot of competition for mind-share in this relatively new space.
Updated 2021 : note that the above post was originally published in 2010, but is left here for archival purposes. I have updated the Riak link to point to their new website.