cxmon is an interactive command-driven file manipulation tool inspired by the "Amiga Monitor" by Timo Rossi. It has commands and features similar to a machine code monitor/debugger, but it lacks any functions for running/tracing code. There are, however, built-in PowerPC, 680x0, 80x86, 6502 and Z80 disassemblers and special support for disassembling MacOS code. cxmon is primarily intended for emulation development but it can be used as a generic tool for manipulating and analyzing binary data and machine code, or just as a hex calculator.
Frodo is a free, portable C64 emulator. It focuses on the exact reproduction of graphical effects possible on the C64, and comes in three "flavors" (Frodo, Frodo PC, and Frodo SC) with increasingly higher quality of emulation, but at the cost of higher processing power requirements. Frodo has been ported to a number of systems, including handheld computers. The Unix version can use either SDL, X11, or SVGAlib to display the graphics.