Some decent choices listed above but I haveMUCH better results with the Termastat Polar Weight series of underwear from Cabela's. You've got to try some of this stuff. Absolutely hands down, THE best I've found. What's most impressive is it's a very thin, incredibly light weight material that doesn't even seem like it should keep you warm in any condition?

http://www.cabelas.com/cabelas/en/templates/links/link.jsp?id=0005027900981a&type=product&cm Cat=search&returnPage=search-results1.jsp&QueryText=thermastat+underwear&am p;N=4887&Ntk=Products&Ntx=mode+matchall&am p;Nty=1&Ntt=thermastat+underwear&noImage=0

http://www.cabelas.com/cabelas/en/templates/links/link.jsp?id=0005027900983a&type=product&cm Cat=search&returnPage=search-results1.jsp&QueryText=thermastat+underwear&am p;N=4887&Ntk=Products&Ntx=mode+matchall&am p;Nty=1&Ntt=thermastat+underwear&noImage=0