There's a tool called [DHEX][1] which may do the job, and there's another tool called [VBinDiff][2].

For a strictly command-line approach, try [JDIFF][3].

  [1]: http://www.dettus.net/dhex/
  [2]: http://www.cjmweb.net/vbindiff/
  [3]: http://jojodiff.sourceforge.net/