libdasm is a C-library that tries to provide simple and convenient way to disassemble Intel x86 raw op-code bytes (machine code). It can parse and print out op-codes in AT&T and Intel syntax.
The op-codes are based on IA-32 Intel Architecture Software Developer's Manual Volume 2: Instruction Set Reference, order number 243667, year 2004. Non-Intel instructions are not supported at the moment (also, non-Intel but Intel-compatible CPU extensions, like AMD 3DNow! are not supported).