Cassandra.IO is a hosted Cassandra Solution that will be offered as part of the Heroku provider addon program.  We are looking for some alpha testers for some feedback and success stories.  

Documentation is scarce right now but we are in the process of setting up a website with some information.  To get an overview of the RESTful API and probably enough to get started take a look at http://m2mio.github.com/

If anyone is interested please send me an email with your Heroku account name.

If there are any questions, issues or comments feel free to reply to this post or email me directly.

Thanks,

~chris