Just came across StuffKeeper.

Stuffkeeper is a generic catalog program. It is not focused on a particular type,  like incollector focuses on notes,logs, chat’s etc, or cdcollector on cd’s, it can hold any type of data.There are programs that can do this, like tellico, but it opens new db for every type. StuffKeeper tries to provide one program, with one view that can show any type of data, in a easy to use and good looking interface.

Linux.com reviews Referencer

Despite its simplicity, Referencer is a useful application that can help you to kill two birds with one stone. You can use the application to organize your documents into easy-to-manage searchable libraries. And the ability to retrieve and manage metadata combined with the ability to handle bibliography files makes Referencer a great tool for researchers and writers alike.

My Ubuntu Blog reviews video collection managers, including Tellico.

Definitely Tellico wins with a clear margin for its intutive approach to manage, display, import, export, search, retrieve and manipulate data.