8mm x 1mm magnets:
My nobz mob with magnets on their bases:
Battle wagon with magnet in the tracks (4 of these smaller magnets work well for the battlewagon):
Magnetized bases
Here's a couple pictures from an upcoming article I'm writing for www.miniwargaming.com. I've put magnets on all the bases of my orks to make them easier to transport. A 30 strong boyz mob will fit nicely into a standard cookie tin, and my battle wagons fit nicely into a larger tin. I've also made a display board that that the magnets will stick to by using magnetic paint. Here's a couple pictures:
