quiltersfleamarket
sewitsforsale
quiltchatclassifieds
sewingnquilting
these are all yahoo groups.
There are many different rules to be able to sell on any of them.
Each has their own rules.
Remember these sites are geared for for selling off your extras, I highly doubt quilt themselves would sell on these groups. I have belonged to them all for many years and not seen quilts even listed. Occasionally a UFO, or BOM or orphaned blocks will though...and machines do well!
You can also go to yahoogroups and do a search of groups that might suit your needs better!