The "Open On-Chip Debugger" provides JTAG/SWD access from GDB (or directly with TCL scripts) to processors with ARM and MIPS based cores.
See website for full list of supported targets.
BEYE (Binary EYE) is a free, portable, advanced file viewer with built-in editor for binary, hexadecimal and disassembler modes. It contains a highlight AVR/Java/i86-AMD64/ARM-XScale/PPC-64 and other disassembler, full preview of MZ,NE,PE,ELF and other.
A standalone powerpc disassembler written as a wrapper over GNU libopcode library. It accepts the opcode ( in hex or decimal ) as it's argument and spits the disassembled output.
Recently, a reference assembler has been added. It takes the instruction in string form and spits the assembled 32-bit opcode.It's not fully tested and may not work always.