I picked up a model M3 Hammond, in very good condition, for $150.00.
That seems to be the going rate, at least in California.  The models
B3 and C3 are still the most sought-after Hammonds.  By the way, if
this Hammond M3 is paired with a Leslie speaker, it will be more
valuable.  In fact, the Leslie loudspeaker is probably worth much more
than the Hammond M3 organ.

There is a Hammond Tone Wheel Ring that lists all kinds of sites
related to these organs:

http://nav.webring.yahoo.com/hub?ring=hammond&list

Sharon Marie