This year, I need to code asm in University.
Well I learned my first bits of asm about 5-6 years ago
So I wrote one.
http://aldis.git.bsdroot.lv/asm4BSD/
It has includes for
lang/fasm and perl script to convert
syscalls.master to fasm format
I will update this project as I need, Maybe it'll be useful for someone else
For generic info about coding in asm on FreeBSD read
http://int80h.org/
Also, what a coincidence, it is described in Latest BSDmag
http://bsdmag.org/magazine/1502-bsd-and-linux
Thread on flat assembler forum:
http://board.flatassembler.net/topic.php?t=11991