Mini-itx computers are amazingly small computers.
They can be powerful machines, they dont take up very much space,
and they are highly modifiable. http://www.mini-itx.com/
is a great site for seeing all of the crazy things people do with
these little devils. If you are looking for ideas of what you can add
to your mini itx machines, then consider some of these options:
Hubs allow you to add more USB peripherals to your computer.
You can add all sorts of ports to your computer by using USB
You can even use USB
Docking Stations to make your work area less cluttered.
Another cool USB add on is a USB
capture device which can allow you to turn your computer into a
Tivo. My personal favorite is the High
Definition TV capture device.
Many ITX computers have PCI slots inside. With a free PCI slot you
can add all sorts of functionality to your computer. You may want to
use your PC as a multimedia center. If you do, then you may want a TV
tuner inside it.
You can check out a plethera of possible PCMCIA
cards that will work with your mini PC.