There are many times and ways you can inadvertently dial your cell phone. Probably the most known one is butt dialing--when you dial random numbers by sitting on your cell phone.
I have thought of another inspired by one of my favorites on FOD (http://www.funnyordie.com/videos/2b6dc10edf/iphone-3g-guided-tour-from-fod-team-and-seth)
Nut dialing--dialing a random number as you rub one out while surfing on your i-Phone3G.
What other inadvertent ways are there?