Pocket PC.
A variation of the palmtop organizer. Only this one runs WinCE, and is much more flexible than a Palm Pilot. Actually, you can run almost anything on a PPC. Most have pentium-compatible CPU and standard RAM. They come in handy when you are trying to organize your calendar, and most synchronize directly with your Microsoft Outlook through USB or Infrared Port, which most PPC's sport nowadays. You can also run a variety of applications which are ported to WinCE, which also allows you to work with a multitude of standard Windows files, including txt, doc, xml, among many others.
Some can even support wireless modems and include Internet Explorer, so you can browse the web from the palm of your hand.
Or you can just shove a 256 MB compact flash card into it, and load it up with music out the wazoo. At least thats what I did, besides do my schedule, edit doc, html and xml files, and play games. Oh, it comes in handy on midterms too!

Also see Pocket PC vs. PalmOS