Bind DLZ on Rails is a Web-based user interface for managing BIND with the bind-dlz extensions on a MySQL 5.0 backend. BIND is a DNS server, and the bind-dlz extensions enhance BIND with support for database backeneds. This simplifies the management of thousands of zones and provides added redundancy (by way of database replication).
Cinabox (Continuous Integration in a Box) automates the setup of a Continuous Integration (CI) system by doing The Simplest Thing That Could Possibly Work. It consists of two simple scripts to set up a cruisecontrolrb CI server from scratch on an Ubuntu 8.04 system: one script to bootstrap Ruby, and another script to set up CI.
Event Calendar started as a replacement for an antiquated script to generate meeting invites with attached ical. It has since grown to be a full fledged event calendar system for public events. Important to Event Calendar is the theory of multiple interfaces, where any data in the system should be accessible in a multitude of ways. For events, this means via nice HTML, iCal, XML, and JSON. Event Calendar also includes integration with Google Maps for directions to event locations.
XapianFu is a Ruby library for working with Xapian databases. It builds on the GPL licensed Xapian Ruby bindings, but provides an interface more in-line with "The Ruby Way"(tm) and is considerably easier to use. For example, you can work almost entirely with Hash objects, and XapianFu will handle converting the Hash keys into Xapian term prefixes when indexing and when parsing queries. It also handles storing and retrieving hash entries as Xapian::Document values. XapianFu basically gives you a persistent Hash with full text indexing (and ACID transactions).