Lafcadio is an object-relational mapping layer for Ruby and MySQL. It lets you treat database rows like first-class Ruby objects, minimizing the amount of time you have to spend thinking about MySQL vagaries so you can spend more time thinking about your program's logic.
The current production release is 0.8.3, and the current development release is 0.9.5. This and older releases can be downloaded from the Rubyforge project file list. The RubyForge project page contains links to stats, discussion forums, mailing lists, and other features.
The manual is available as one HTML page, and broken up into sections. There is also RDoc class documentation available.