Other computer interfaces: beyond Arduino
In the exhibit world, these are fairly common:
— switch-to-keyboard emulator (note that there is a USB version).
Also, along the same lines, I *heart* Teensy’s
which you can very easily (and in the Arduino environment) program to be a virtual USB keyboard.
Also as Dr. Jesus mentioned the FTDI chips are good… and there are FTDI chips made specifically for parallel interfacing,
and for very fast IO…
Another option is the BitWhacker — you can build your own or pick one up from SparkFun pre-programmed.
I also have friends who love LabJacks.
and for low pin count interfacing, there’s always the BusPirate
Get a AVR usb dev board (AT90USBKEY2, $30 at the usual places), and
with the LUFA open-source USB stack, you can make the board look like
a USB HID keyboard (or mouse, or…) such that any input pin change
can generate any arbitrary key events you want. No drivers, no hassle,
should wake up a sleeping box just like a regular USB keyboard.
If you’re down for even more microcontroller hacking, the ATTiny series can be convinced to bitbang USB, including HID: http://www.xs4all.nl/~dicks/avr/usbtiny/
You’ll probably want to use an ATTiny2313 if you want more than 3 inputs without doing dirty ADC, mux, or shift register tricks.