Are there listservs devoted to other specialiazed music and recording interests where records for sale listings are welcome?  They will include 78s, LPs, transcriptions, related books, record catalogs, etc.   I'm thinking of classical, (particularly strings, chamber music, 20th century music, organ, opera, art songs in all languages), older pop, lighter jazz, theater organ, etc.  
So far, I've just
78 c
88s on 78s (classical piano)
Steve Smolian