Ruby Reports (a.k.a. Ruport) is a free library and toolset for Ruby that makes building reporting applications easy developed by Gregory Brown. It's available under the Ruby and GNU GPL 2 licenses.
Ruport can acquire data from databases and files and provides tools to manipulate the data as necessary for the required reports which it can output in HTML, PDF, CSV and plain-text formats (also to e-mail). Ruport is undergoing constant development and also has an IRC channel at #ruport on irc.freenode.net if you want to speak to the developers directly. As an ongoing project, Ruport is looking for more contributors and developers, especially those with experience of reporting and data manipulation.