As I was looking for a COFF Browser today (a tool that would show me the internals of a DLL or EXE file) I stumbled upon a page talking about Assembly Language and the GoAsm tools.

The page is here: [page was removed]

Interestingly enough, he has a link to an advanced assembler called GoAsm. This is specifically for MS-Windows and they do not release the source code of the assembler (at least, not that I can see...) But it is still interesting to see such tool suite around. 8-)