Favored Freeware: SimpleViewer

SimpleViewer is a free, customizable Flash image viewing application.

SimpleViewerAdmin is an administrative web interface which allows you to create multiple galleries, upload images and automatically generate thumbnails.

Pros: SimpleViewer is a simple gallery. Using it is very much like having your own Flickr, but without the fluff.

Cons: SimpleViewerAdmin is almost a requirement. Without it, SimpleViewer is very cumbersome to use.