Ruby appscript (rb-appscript) is a high-level, user-friendly Apple event bridge that allows you to control scriptable MacOS X applications using ordinary Ruby scripts. It is a port of the powerful, mature Python appscript package, making Ruby a serious alternative to Apple's own AppleScript language for automating your Mac.
rdiff-backup backs up one directory to another. The target directory ends up a copy of the source directory, but extra reverse diffs are stored in a special directory so you can still recover files lost some time ago. The idea is to combine the best features of a mirror and an incremental backup. rdiff-backup can also operate in a bandwidth- efficient manner over a pipe, like rsync. Thus you can use rdiff-backup and ssh to securely back up to a remote location, and only the differences will be transmitted. It can also handle symlinks, device files, permissions, ownership, etc., so it can be used on the entire file system.
reSIProcate is a high performance, object-oriented, C++ sip stack that is compliant with RFC 3261. It includes support for a wide variety of operating systems, including Windows and Linux. It has full support for UDP, TCP, and TLS transports on both IPv4 and IPv6. It also implements the full set of specifications for DNS usage in SIP, including NAPTR and SRV lookups (RFCs: 3263, 2915, 2782) using an asynchronous DNS library (ares).
reacTIVision is a computer vision framework for the fast and robust tracking of fiducial markers attached to physical objects, as well as for multi-touch finger tracking. It was mainly designed as a toolkit for the rapid development of table-based tangible user interfaces and interactive multi-touch surfaces such as the reacTable. Client application examples are available for various programming environments such as C++, Java, C#, Processing, PureData, Max/MSP, and Quartz Composer.
recorder.xhead is a voice recording application that can save sounds in .mp3, .mp4, .aif, .avi, .mov, or .wav format. Users can create a playlist of recorded sound, search it iTunes-style, and even export it to iTunes so that they can take voice memos on the road on an iPod. It plays audio streams, and comes with a bulk file conversion utility to convert between file formats.