Object Code Translation Home Page - Some introductory discussion of disassembly. Also has a glossary, and short description of file formats. Many links to other resources. - http://www.ifi.unizh.ch/groups/richter/people/pilz/oct/
Clive Turvey's Home Page - Source for a commercial disassembler and a selection of free downloads related to disassembly. Also has a useful collection of links to related sites. - http://www.tbcnet.com/~clive/vcomwinp.html
Giampiero Caprino's Home Page - Contains useful information about Decompilers and File Formats. - http://www.backerstreet.com/cg/work.htm