In assembly language, your best resources are on the web.
http://www.linuxassembly.org/ - a great resource for Linux assembly language programmers
http://www.sandpile.org/ - a repository of reference material on x86, x86-64, and compatible processors
http://www.x86.org/ - Dr. Dobb's Journal Microprocessor Resources
http://www.drpaulcarter.com/pcasm/ - Dr. Paul Carter's PC Assembly Language Page
http://webster.cs.ucr.edu/ - The Art of Assembly Home Page
http://www.intel.com/design/pentium/manuals/ - Intel's manuals for their processors
http://www.janw.easynet.be/ - Jan Wagemaker's Linux assembly language examples
http://www.azillionmonkeys.com/qed/asm.html - Paul Hsieh's x86 Assembly Page