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.
rdp2tcp is a tunneling tool on top of remote desktop protocol (RDP). It uses RDP virtual channel capabilities to multiplex several ports forwarding over an already established rdesktop session. Its features include TCP port forwarding, reverse TCP port forwarding, process stdin/stdout forwarding, and SOCKS5 minimal support.
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.
reciteword is education software developed using GTK 2 to help people study English and recite English words. It has a very beautiful interface to make reciting words an interesing thing. It can change skins, and comes with many sound events, including over 400 books for you to choose. It also includes a dictionary, which can also run separately.
Roap is a text file processor. It scans a text file, extracts regions that match specified patterns, and processes these regions sequentially using specifed executables. Each executable reads the region as stdin, and their combined stdouts are written as the stdout of Roap. Patterns and executables are specified using XML.
reversible hexdump is a hexdump/hex2bin-toolkit that dumps to a special readable and reversible hexadecimal byte-dump, where you can not only change bytes, but also insert or delete bytes. It has a flush-switch, where it will output hexbytes for each single char it reads. This is especially useful (imho) for watching output from slow devices (e.g., serial devices like mice). The hex2bin-utility (the reverse-hexdump) not only accepts hexbytes for input, but also double-quoted strings with most of the escape-chars known from C and makes good attempts at undumping even hexdumps with repetition-lines (a "*" on its own line). It's written in ANSI C.