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.
While the OSS community converges to Git, with the Python bunch branching to Mercurial, the typical workplace is stuck with Subversion. The author's DVCS of choice is Fossil. These are all fine projects, with their own pros and cons, but what you usually want is just a tool to store your code tree snapshot in a safe place. They can all do that, but their language differs a tiny bit. repo brings them all down to the common root. It works by detecting which VCS are you using right now and calling that, applying necessary subcommand translation if needed.
rioutil is a utility designed for the use of interfacing with Sonic Blue/dnna's third, fourth, and fifth generations of flash MP3 players (Rio 600/800/900/S-Series/Riot/Cali/Chiba/Fuse and Nike psa[play). On many players, it goes beyond the packaged software by providing downloading.
rlimit is a program that lets you run processes with system resource limits set. It can be used by software developers and testers to test that software will run correctly in resource restricted environments. It is also useful for software which would otherwise consume excessive resources such as programs that used 100% CPU, set their own priority levels, or consume too much memory. This is basically a command line interface to the system functions getrlimit() and setrlimit().
rsyncbackup is a handy tool for scheduled backups using rsync. rsyncbackup lets you easily setup multiple source folders and destinations, both locally, on your iPod or external firewire disk, or at a remote destination using ssh. rsyncbackup has no GUI, but is based on editing configuration files. The script is meant to be run in a crontab, so user interaction is not neccesary. Basic terminal skills are required to use the program.