Sequel is an ORM framework for Ruby. Sequel provides thread safety, connection pooling, and a concise DSL for constructing queries and table schemas.

This release solves issues pertaining to SQLite and MySQL transactions, adds a Dataset#exclude method, and a great enhancement for refining conditions, so now you can do stuff like:

posts.filter(:category => 'Ruby').exclude(:author => 'David')

For more information have a look at the docs:
http://sequel.rubyforge.org