I'm considering selling off a successful freeware/shareware application to another developer. It has a decent userbase and a reasonable income (for an app with zero advertising).
For more info, see some of the details in the MacNN Market Place forum at:
http://forums.macnn.com/showthread.php?t=252060
and PM me for specifics after that.
(I've posted here in addition to the Market Place, as I've had little response so far and I don't think many people expect software development projects to come up for sale there often).