reken is an command-line calculator based on a C coded expression evaluator. It can use user-defined functions and variables. Functions can be integrated (numerically) and differentiated (numerically). An input file can be used for complete calculations or to set up the command-line environment before use (things like PI and some standard functions can be set). Integrating is not fast and not very precise, but should suit hobby calculation needs.
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.
RMP allows remote control over playing your music files on a Linux computer. The music can be controlled via a Web interface, a smart cellphone, iPhone, Blackberry, or through a command line shell interface. If you like the song, you can download it to your phone. It supports next, searching, and volume control.
rmutt is a utility for generating random text from context-free grammars (a.k.a. recursive transition networks). It's modeled after Andrew C. Bulhak's late, great "dada engine", which he used to write the hilarious Postmodern Thesis Generator. rmutt takes as input a set of user-supplied grammatical rules, each of which represents a set of choices that can be made at a particular level of grammatical description. For instance, a grammar might specify that a "person" can be either "Fred" or "Jennifer". rmutt then makes these choices randomly, resulting in text which conforms to the grammar but is otherwise unpredictable. Grammars in rmutt need not relate in any way to the grammar of any human language. For instance, rmutt can be used to generate text instructions for producing graphics or music. rmutt is similar to the dada engine in that it allows for contextual behavior. In other words, its grammars are not actually context-free. For instance, a choice made in one rule may affect the definition of another rule. Also, textual transformations can be applied to the output of rules.
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.