ToACME is a simple command line utility to convert source code files from other assemblers' formats to ACME format.
The current version (0.9) supports these formats:

Input format	Output quality
(C64) AssBlaster 3.0 to 3.2	good
(C64) Flash8-AssBlaster 1.0 to 1.2	ok
(C64) Hypra-Assembler	ok
(C64) Giga-Assembler	ok
6502 object code	poor

Here are the sources of the newest version:
Download C sources (Release 0.9, now with working converter for Giga-Assembler sources)
Download C sources (Release 0.8, now with useable converter for Giga-Assembler sources)
Download C sources (Release 0.7, now with working converter for Flash8-AssBlaster sources)
Download C sources (Release 0.6)
Download C sources (Release 0.5)
Binaries will follow RealSoonNow.

Have fun!