Gallery1 is an open source image gallery system. Gallery1 was succeeded by Gallery2, though is still updated. Gallery1 installs can be upgraded to Gallery2 via a Gallery2 plugin.
From the Author
Gallery lets you manage your photos on your own website.
With Gallery you can easily create and maintain albums of photos via an intuitive interface. Photo management includes automatic thumbnail creation, image resizing, rotation, ordering, captioning, searching and more. Albums can have read, write and caption permissions per individual authenticated user for an additional level of privacy. Give accounts to your friends and family and let them upload and manage their own photos on your website!
Authors website: http://gallery.menalto.com