Over the past 9 months, we've learned a lot about indexing in Cassandra and we've had a few false starts.  I've tried to capture what we learned in the hopes that we can save a few others from false starts.

http://brianoneill.blogspot.com/2012/03/cassandra-indexing-good-bad-and-ugly.html

We've also released some code in the hopes of making it easier to implement wide-row indexes.
https://github.com/boneill42/cassandra-indexing

Its more AOP code (just like our cassandra-triggers) that implements wide-row indexing for you.
Just configure which column families you want indexed, and on which columns you want the index and let the AOP take care of the rest.
It is still very much in its infancy, but as always -- comments are welcome.
(especially if we have something wrong ;)

-brian

--
Brian ONeill
Lead Architect, Health Market Science (http://healthmarketscience.com)
mobile:215.588.6024
blog: http://weblogs.java.net/blog/boneill42/
blog: http://brianoneill.blogspot.com/