GHEX is a simple binary editor, allowing the user to view
and edit a binary file in both hex and ascii with multiple
level undo/redo mechanism. It features find and replace
functions and conversion between binary, octal, decimal
and hexadecimal values, making use of an alternative,
user-configurable MDI concept to allow the user to edit
multiple documents with multiple views of each.

WWW: http://www.gnome.org/