Is the International Residential Code available online, free, anywhere? If not, is there anything equivalent available -- at least good-enough for a DIY builder?

Looking at Abebooks I see that I can get 2000 and maybe 2003 or 2006 versions for less than $15.

http://www.abebooks.com/servlet/SearchResults?sts=t&tn=international+res...

How much different are these older versions compared to the latest version? How helpful is it to a DIY builder to have access to the International Energy Conservation Code?