After some research on NoSQL databases, for a future rails project, the projects that caught my attention were:

I’ve spent some more time MongoDB. Their list of prodution deployments is impressive. John Nunemaker developed an adapter for ruby, the MongoMapper, which already supports some neat features like validations and callbacks, much on the ActiveRecord style. See this article and the presentation below for more info:

Still have to spend some time experimenting with it, but it seems promising. 

Has anyone tried NoSQL with rails, on a recent project? Thoughts to share?