My feeling is that my oil plugs have come out more easily when the engine is hot (rather than warm or cold). I suspect the oil pan threads are more flexible when hot so they are less likely to be damaged - but I don't know much about metals.
Heat and "Liquid Wrench" penetrating oil and rapping are the first things are I try, when removing a stiff bolt. A propane torch can help but make sure you don't set something important on fire. The Liquid Wrench is probably useless but it can't hurt.
When your plug comes out, inspect it for bad threads or damage. Don't reuse it if not perfect.
Hey where can I get a magnetic oil plug? If I stick 1-2 of my tiny "rare-earth" magnets on the end of my original plug, would that be good enough to attract iron bits? I don't think there's any other magnetic metals near the plug but not sure.
Here is a link to the type of magnet
http://www.dealextreme.com/details.dx/sku.4248 that I am talking about, maybe 10mm would work also - they are used for spacing out and sticking flashlight batteries together while maintaining electrical contact.