vcprompt prints a short string, to be included in your shell prompt, with barebones information about the current working directory for various version control systems. It is designed to be small and lightweight rather than comprehensive. It has varying degrees of recognition for Mercurial, Git, Subversion, CVS, and Fossil working copies.
Qataki is a shell script that you can use to read/post notices from the command line in a simple manner. It supports Identi.ca, Twitter, and StatusNet. You can post, reply, retweet, or send direct messages; read personal, public, and user and group timelines (last statuses); read messages directed to you (i.e. where you are mentioned); read messages in context (conversations available only for Identi.ca/StatusNet); and search for notices.
audiopreview is a command-line tool that plays previews of many audio file types (Ogg, MP3, etc.), video file types (AVI, MPEG, Real, etc.), and Internet streams. It can also be used as a regular command-line media file player (i.e. play the files entirely like yauap or mpc123 would).
Autojump is a tool that acts as a complement to cd: it makes navigating your filesystem a lot faster. It works by automagically maintaining a database of the directories you use the most from the command line, and allows you to jump back and forth between them, by typing just a few letters of the name of the directory you want to jump to. It works for Linux, Mac, and Cygwin under Windows.