I haven't done a fursuit yet (someday!) but I make animal sculptures using techniques that might be helpful for fursuit makers. In the description under the picture are links to the step by step process of making this. http://www.deviantart.com/deviation/29028391/
Basically I laminate and carve the pink high density poly foam insulation from home improvement stores. It's more economical and durable than other materials. (harder to carve than the white foam though) Details are sculpted on with epoxy putty and the eyes are glass taxidermy eyes. I airbrushed the fur on this one for realism. This technique would probably make a more realistic looking fursuit head than many of the other techniques I've seen, it just requires a lot of carving.
The only problem with the pink foam insulation - it traps a lot of heat, naturally. But I think the other types of foam do too.
I hope these techniques can help someone out. ^^ Any questions, just ask. Gotta be nice so you guys will help me out when I finally make my fursuit. ;) Considering that I don't even know how to sew, I'm going to need lots of advice.