What is a Zaurus? It is a neat PDA (personal digital assistant) sold by Sharp. The cool thing about it is that it does not run Windows, but a UNIX-clone. To be exact, it runs a Linux variant known as "Embedix". Personally, I would prefer a BSD operating system (FreeBSD or NetBSD), but well, no PDA is perfect ... And the Embedix on the Zaurus turned out to run quite smoothly.
Of course, since it runs Linux, it runs almost every UNIX application in existance. Just a few examples:
Install OpenSSH. Then you can not only connect from the Zaurus to other machines, but you can also connect from somewhere else to your Zaurus. There's also telnet and telnetd already installed by default (telnetd isn't enabled in inetd.conf, though), but you really want to use ssh for security reasons.
You can install a VNC client as well as a VNC server. Why install a VNC server? Well, because it enables you to control the Zaurus completely from your desktop PC, which is really convenient when you want to enter large amounts of text. (The tiny keyboard of the Zaurus is usable, but not really as convenient as a real one, and the Zaurus' handwriting recognition is not perfect.)
Multimedia applications. Image viewers, audio players, movie players (a simple MP3 audio & MPEG1 video player is pre-installed, but there's also a port of mplayer for the Zaurus, so you can watch MPEG4/DivX AVIs etc.), image drawing tools, audio recording, and so on.
PIM applications (personal information management). The basic tools are already pre-installed: clock, calendar, address book, to-do list, calculator, memo text editor, e-mail.
Programming. There's a gcc crosscompiler (for developing Zaurus programs in C or C++ on your PC), a native gcc package (for compiling directly on your Zaurus), the are precompiled packages for Python, Perl, AWK, LISP, Scheme, Haskell, and more. A Java runtime is already included with the Zaurus. And of course, there's /bin/sh (actually a Linux-typical bash) for writing shell scripts.
Emulators. There is a C64 emulator, an Atari emulator, a ZX Spectrum emulator, emulators for MAME (for video console games), ScummVM (for LucasArts adventure games such as Monkey Island, Day Of The Tentacle, Sam & Max), and of course a GameBoy emulator.
Games. There are really lots of games: board games, card games, action games, strategy games, adventure games, etc. Just to mention a few of the "classics": Chess, Go, Checkers, Backgammon, MineSweeper, PacMan, Tetris, Breakout, Mahjongg. Of course, there's a port of NetHack, and a port of DooM (with stereo sound and network support, of course). Imagine playing DooM with (or against) another Zaurus owner on the bus ...
Install a terminal emulator (VT100) and use the Zaurus as an emergency serial console for your server farm. (Requires a serial cable which is sold separately.)
You can use it as a server. In fact, there are precompiled Apache packages and others. Imagine you meet some guy with a notebook in the subway, he notices your Zaurus, and you demonstrate a few features, for example, you show him an MPEG movie stored on the Zaurus. The guy would like to have a copy of that movie on his notebook, so you tell him to set up a WaveLAN connection, fire up a webbrowser and enter http://your.zaurus.ip/ to access the webserver on your Zaurus ... (if you don't happen to have WaveLAN cards, use PPP over IrDA instead, although that would be slower).
Here are a few pictures (click on them to enlarge). Note that the Zaurus has a tiny built-in keyboard, which can be opened by pulling down the lower part. Of course, you can also enter text by writing on the display (the handwriting recognition isn't perfect, though), and there's also a virtual on-screen keyboard available.
Here's a bunch of screenshots.
If you're interested how the Zaurus can be connected to the Internet (or to a private network), look at my Zaurus Ethernet page.
Finally, I have collected some Zaurus links on a separate page.