I haven't gotten my R-Pi yet, otherwise I would've just tried it, but do I need a ribbon cable to use GPIO or can I just connect a bunch of wires from the pins to a solder-less breadboard?
I've mostly been using individual wires, you can just connect the ones you need.
Unless you are doing really high speed IO you shouldn't need to take any special measures.
As usual things work less well as the wires get longer and longer, so driving 100m wires straight from GPIO may or may not work. 20-100cm should be no problem though
The inexpensive wires I've been using you can find by searching for "40 way arduino" on ebay.
You can easily break off a bunch of wires or use them individually
Bunch of wires is fine. You must connect GND, don't source current from the 3V3 pin and the pins aren't 5V compatible.
Just wanted to share how I did. Found an old A: (disk drive) flat cabel, connected it to the pi in one end and the other to the bread board. At the bread board end I put some metal thread between the output of the flat cabel and the input holes in the board (inexpensive).
Here one can see the metal going from the cabel to the boad.
It is risky to wire so close to the rPi board.
Using an old IDE ribbon cable is less risk.
I use an Adafruit Pi Cobbler Breakout to breaks out rPi pins onto a breadboard.
Individual crimp pins in heat shrink work well.
A wire wrap tool can also be very handy for interconnecting boards in prototype systems - although not designed for it, it will typicall work on 2mm headers as well.