BreakPoint Software, Inc.
   Home of Hex Workshop, the Professional Hex Editor (and sector editor, base converter, and bit manipulator). [Commercial]
   http://www.bpsoft.com/

Hackman
   An advanced hex editor and disassembler. News, support and related products such as language packs, plugins and add-ins.
   http://www.technologismiki.com/hackman/

HexTool
   A small and fast binary file and hex editor for DOS, with mouse interface. [Shareware]
   http://www.durward.com/hextool

Shed
   Easy to use hex editor written for Unix/Linux using ncurses, with a friendly pico-style interface.
   http://shed.sourceforge.net/

The HT Editor
   A professional executable file editing tool which currently supports the MZ, PE and LE file formats including code analyser. For Windows and Unix. [Open Source]
   http://hte.sourceforge.net/