ruby update is a ruby script which helps people who install their packages from source keep their packages up to date. It does not attempt to install anything on its own, but simply scans your file system and lets you know if there is an updated version of a particular program. rupdate can only check the status of those programs for which it has been hard-coded to check.
Virt-Factory is a framework for managing a large number of Xen virtual machines, such as might be found in data centers or large lab configurations. It works by managing a pool of registered physical hosts and then deploying virtual machines, which have specific roles as defined by their "profiles" (profiles act as shareable virtual appliance definitions), onto those hosts. Virt-Factory provides both a Web UI (for ease of use) and an XML-RPC API (for scripting of admin actions). A command line interface (along with other advanced batch management features) is coming soon.
BitNami RubyStack provides a fast, easy way to develop and deploy Ruby on Rails applications. It includes Ruby, Subversion, MySQL, SQLite, ImageMagick, and several Ruby Gems, and will optionally install Apache 2.2 with rewrite and proxy support. It supports Windows, Linux, and OS X, so you can share the same Rails environment on multiple platforms.
MrTools is a suite of tools for managing large, distributed environments. It can be used to execute scripts on multiple remote hosts without prior installation, copy of a file or directory to multiple hosts as efficiently as possible in a relatively secure way, and collect a copy of a file or directory from multiple hosts.