Binary Editor Applications

http://www.sweetscape.com/010editor/ WOW! A real binary STRUCTURE editor with scriptable decompilation AND EDITING of any binary format. Probably the nicest user interface I've ever seen. Very reasonable price. Be sure to send them any structures you define so they can build a nice big library of templates. Just excellent!
http://www.nyangau.fsnet.co.uk/ A binary structure editor. Powerfull, runs on several OSs. Character based user interface. No floating point or Unicode, and most importantly, structures of variable length are really hard to support. hint: look at the validity test. Best bet for the Linux crowd.
http://www.pbsoft.com HexWorkshop. Basic functions, some structure support. Buggy.
http://www.ultraedit.com/ Text, HEX, database editor with ftp, templates, regular expression search and replace, column edit, spell check, conditional macros, keyword highlighing. syntax macros and keywords for HTML, ASP, VB, Java, Perl, C/C++, PIC, etc... Wierd insert and delete in HEX mode makes it useless for binary. No structure support.
http://www20.brinkster.com/ewayne/AsmLoad.html (cached 20011030091557) designed for editing win32asm source, it can also edit binary files as raw hex (no structure support). Open source, written in pure assembly. Not for the faint of heart.
http://www.kahei.com/ AXE Binary Hex editor with some structure support. {ed: domain sold in 2000, the link is to wayback, but the actual program was not archived as far as I can tell. Please let me know if you have a copy of this program}
EdCom42 A86 Assembly Source, full screen dos binary editor with x86 de-complier {ed: lost... try simtel?}