Overview

Piwigo is a photo gallery software for the web, built by an active community of users and developers. Extensions make Piwigo easily customizable. Icing on the cake, Piwigo is free and opensource.
Features

select your photos and transfer
pLoader, the remote client
FTP
synchronize
several servers
category tree
flatten
set permissions on each category
Tags
related tags
chronology
calendar
best rated
most seen
random set
multiple criteria search
the slideshow
comments
users
permissions on photos and categories
notified of news by email or by RSS
groups
user levels
user comments and rating
EXIF and IPTC
pretty URLs
history statistics
history can also be filtered
localization
customization
themes and templates
web API