Photo Viewers.
I’m on a Macintosh running OS X. I really appreciate the iLife applications. Unfortunately, for a graphics professional, there are several aspects that make iPhoto difficult to manage a dynamic collection of images. I have many images in multiple places on my system, and keeping images in the original folders is very important. When importing images into iPhoto, files are copied into the iPhoto folders. This needlessly takes up disk space with duplicated images. An earlier version of iPhoto had a tab for applying keywords. Moving this to a palette has deminished the original functionality. iPhoto is fantastic for managing personal photos, and works for this very well. I’ve done a search and found several other applications to view and manage images. NattaWork’s PhotoGridX and Caffeine Software’s Curator.

PhotoGridX.
Features include: search for images in any directory you select, automatically generates thumbnails, (some applications are so sensitive to performance issues related to rendering thumbnails you need to specifically create them), detailed image details, and slide show.

Curator.
Caffine Software is out of business, so any software is absolutely unsupported. Features include: OS X-like column file viewer, custom albums, build web page feature, add comments, keywords, and slide show.