Opdis is a wrapper for the libopcodes disassembler library distributed as part of GNU binutils. It extends the libopcodes library by offering linear and control-flow disassembly algorithms, instruction and operand objects that are suitable for analysis, and a command-line utility to perform disassembly on arbitrary locations in a file.
The Opdis project consists of the libopdis library and the opdis command-line utility.
Opdis man page:
http://community.thoughtgang.org/content/opdis/doc/opdis.1.html
Libopdis API documentation:
http://community.thoughtgang.org/content/opdis/doc/api/index.html