Would be great to have a layout for this circuit:
http://www.diystompboxes.com/smfforum/index.php?topic=101580.0It's a clean sub octave, which should sound great on its own or with a fuzz for a "stoner" sound.
That IC is obsolete, but easily available. It's been used in the DOD Meatbox and in the early Ashdown ABM bass amps as well.