Lisa,
It may not be for you, however, you might look at my post on building a DAM system for photos. DAM is short for Digital Asset Management (a fancy way of saying digital photos).
My own search for a low cost, easy to use DAM system was fruitless -- so I build a simple one. There are other solutions, but this one was easy, elegant, and I already had SharePoint.
I describe how to build one using the free version of Windows Sharepoint Services (v3). It's web based, so macs can play too. But, it requires Windows Server 2003 and IIS as the hosting OS/web server. It's based on the built in support of a "picture library." As a result, there are a lot of tools and integration stuff with Office that make it really easy to use, easy to train, etc.
Look here: http://www.digitaldiner.org/2007/03/28/dam-pictures/
Regards
Gavin
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Gavin Clabaugh
Sometimes blogging 
www.digitaldiner.org
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-----original message-----
>>I am seeking recommendations for digital photo archiving software for small-ish non profits without a lot of photography or IT expertise. The software should enable them to archive thousand of images with date, rating, tagging, etc. in an easy and intuitive way. I work on a Mac and love iphoto and aperture, but am looking for something for PCs to recommend to the orgs we work with. Any suggestions?>>
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