Vanxmedia.com
Washago Web Design is a Web Development firm located in Toronto Ontario, Canada. We specialize in Macromedia Flash websites.
http://www.vanxmedia.com

BookmarkDD
It notices when duplicate bookmark is added.
http://bookmarkdd.mozdev.org/

S & J CD Duplication, Inc.
At S & J CD Duplication we specialize in all areas of CD and DVD Duplication, CD and DVD Replication, and CD and DVD Manufacturing for CD-ROM, Audio, DVD Video or DVD-ROM.
http://www.snjcd.com/

RFC 1047
Duplicate Messages and SMTP. C. Partridge. February 1988.
http://tools.ietf.org/html/rfc1047

ResourceBooker
Allows you to book and schedule shared resources thus preventing duplicate bookings.
http://www.resourcebooker.co.za

RFC 0677
Maintenance of Duplicate Databases. P.R. Johnson, R. Thomas. January 1975.
http://tools.ietf.org/html/rfc677

Find Duplicates
Find Duplicates
http://geocities.com/hirak_99/goodies/finddups.html

WebConfs
Duplicate content validation tool and search engine spider simulators.
http://www.webconfs.com/

aptsamever
Lists or removes old duplicate versions of packages installed by apt-get. Downloads provided.
http://aptsamever.sourceforge.net/

Coptech Inc
Coptech Digital offers the best in CD duplication, DVD duplication and print solutions. No matter who the client or how complex the job, we provide comprehensive personal support and consultation on every project and we stand behind our work 100%.
http://www.coptechinc.com/