Gary,

>Does anyone know of any good merge/purge routines/algorithms/third party products? I have the classic problem of dupes in a mailing database. Thanks.

check out http://www.software-datatools.com

DoubleTake is powerful and very customizable. SuperDup is simple to use and does a very respectable job, if more limited in it's options.

Amazingly enough here's really not much competition out there in the PC market, except for de-duping built into other software, like most CASS software.