Unicorn is a Unix and LAN/localhost-optimized fork of the Mongrel HTTP server. It takes full advantage of functionality exclusive to Unix-like operating systems. It will reap and restart workers that die from broken apps, and there is no need to manage multiple processes yourself. Load balancing is done entirely by the operating system kernel. Requests never pile up behind a busy worker. The server does not care if your application is thread-safe or not, as workers all run within their own isolated address space and only serve one client at a time. All Rack applications are supported along with pre-Rack versions of Ruby on Rails via a Rack wrapper. It also supports atomic log cycling, nginx-style binary re-execution without losing connections, before_fork and after_fork hooks, and optional copy-on-write-friendly memory management.
Rainbows! is an HTTP server for sleepy Rack applications. It is based on Unicorn, but designed to handle applications that expect long request/response times and/or slow clients. For Rack applications not heavily bound by slow external network dependencies, consider Unicorn instead as it simpler and easier to debug.
PerfMonger is an yet another performance monitoring tool. The monitoring targets of PerfMonger are similar to the ones of sysstat (CPU usages, IO usages, etc.), but PerfMonger can collect and report performance information very frequently (the reporting interval of sysstat is 1 second at minimum, but PerfMonger can use a much smaller interval such as 0.5 seconds or 0.01 seconds) and can display performance information in both human-readable and machine-readable formats.
libguestfs is a set of tools for accessing and modifying virtual machine (VM) disk images. You can use this for viewing and editing files inside guests, scripting changes to VMs, monitoring disk used/free statistics, P2V, V2V, performing partial backups, cloning VMs, and much more. libguestfs can access nearly any type of filesystem including: all known types of Linux filesystem (ext2/3/4, XFS, btrfs, etc.), any Windows filesystem (VFAT and NTFS), any Mac OS X and BSD filesystems, LVM2 volumes, MBR and GPT disk partitions, raw disks, qcow2, CD and DVD ISO images, SD cards, and dozens more. libguestfs doesn't need root permissions.
The virtualbox-COM Ruby gem is a library that provides a low level Ruby binding to the VirtualBox API, allowing anyone to control VirtualBox from Ruby code. It can create, destroy, start, stop, suspend, and resume virtual machines, and also list virtual machines, list hard drives, network devices, etc.
Redmine is a flexible project management and issue tracking Web application. It supports multiple projects, flexible role based access control, Gantt charts and calendars, news, document, and file management, feeds and email notifications, per-project wikis and forums, time tracking, custom fields for issues, time entries, projects, and users, SCM integration (SVN, CVS, Git, Mercurial, Bazaar, and Darcs), issue creation via email, multiple LDAP authentication support, user self-registration support, multi-language support, and multiple database support.
Marathon is a GUI test tool that allows you to play and record scripts against a Java Swing UI. It's written in Java, and uses Python and Ruby as its scripting language (the emphasis being on an extremely simple, readable syntax that customers/testers/analysts feel comfortable with). Marathon includes a recorder, editor, player, and debugger to simplify working with test scripts.