It's official: the 10gen open source cloud computing platform
(http://www.10gen.com) now supports Ruby and Rails. See the blog post
for details and links to documentation, the SDK, mailing lists, and
The 10gen platform includes a multilingual app server and distributed
document database. You can grab the source or download a pre-built
SDKs from the Web site.
Note: the Rails support does not yet include ActiveRecord. We're
working on it. In the mean time, you can access the database via an
AR-like set of classes or "raw".