Let's Make Robots!

Arduino, holding wires in without soldering?

So I am building/ working on my robot, http://letsmakerobots.com/node/24204 and I didn't want to solder the wires into my arduino. Whenever I moved robot, the wires come out of the pins. Currently I am using scotch tape, I know not very professional. I was wondering if there is any other way to keep the wires from coming out?