xa (aka xa65) is a Mostech
6502 family
cross assembler originally written by
Andre Fachat. It's one of the few
GPLed cross-assemblers that make programming
Commodore 64 more fun.
Hacking assembly with XEmacs is much more fun than when using Turbo Assembler's clunky editor... or something equally sinister. Plus, my P166 running Linux compiles code a bit faster than my C64...