AmosPro supports extensions written in 68k Assembly language so, if you don't mind sticking with hardware-banging classic Amiga code, head on over to the Amos Factory website and sign up. Once you sign up you get full access to the download archives including the .adf files of original AmosPro install disks.
Yeah, AMOS rocks.
I am currently working on an "Extension Creation Guide" as there are things that Francois Lionet (creator of AMOS and STOS) didn't comment on in his guide (either in full or in part).
If I can pick up assembly code (I am an experienced BASIC programmer since the early 90's) in a few weeks (with the help of a few good books - an ASM guide and the Amiga RKRM's), then so can anyone else!
Regards,
Lonewolf10