While looking for something else entirely, I tripped over some general computer knowledge pages at http://vlaurie.com/ which included the surprising bit of trivia that there is a kind of font editor shipping in XP, but not well known.
It is the Private Character Editor, and is intended to allow an end user to design characters in the Unicode range dedicated for private use. This is the recommended place to put a company logo character, for example. Apparently, there is a mechanism in place in Windows to allow characters built in this tool to be logically attached to individual fonts.
The private character editor is not found in the start menu. To launch it, click Start, Run, type eudcedit in the box and click Ok. If you want to create a shortcut to it, it seems to live in %SYSTEMROOT%\System32\eudcedit.exe
The private characters can be retrieved for use in a document with the aid of Character Map. Of course, once you use a private character in a document you are faced with a different dilemma, namely how to let anyone else use the character too... I'll leave that as an exercise to the reader.