[mahmud]

Here is the official website. The author has been actively evangelizing free access to his materials since the early 90s.

http://www.artofasm.com/

Randall Hyde is a legendary educator, hacker and active member x86 assembly community.

[e12e]

It's a great resource, I just wish there was a version targeting amd64/Linux -- it's such a much more pleasant target to write asm for than x86 (not to mention if you target running code under "regular" OS', it's a more and more relevant target).

[easytiger]

Err, that aoa books are incredibly controversial in approach however. The HLA stuff undermines the goals of most people trying to learn it.