A COMPLETE GUIDE TO HERALDRY by Arthur Charles Fox-Davies has been put online—didn’t know if it’s been noticed here yet (and if it has, I couldn’t find it before I posted)
That’s pretty cool. My copy is pretty rough looking since I got it used, but it contains a lot of great information.
Just to tag along with this thread, if you go to Google Book and do a search for heraldry, there are a lot of books that are available for free download in PDF format.
Here is a listing of all o the free e-books on Google with just the keyword "heraldry"
www.archive.org also has a lot of heraldry books in several languages