open source

Gallery is a high quality web based photo album organiser. It can organise photos, audio files and videos into albums and has a number of helpful features such as automatic image watermarking and e-commerce.
Not unlike Drupal, Gallery has many modules which can be installed as needed to suffice the needs of users and site owners, but without 'bloating' a website with too much complexity.

Drupal is an open source content management system or CMS for short. Drupal allows users to manage content of a website, such as articles and images. Many features, such as forums, shopping carts and blogs, can be added from the large collection of modules provided by the open source community free of charge.
This makes for a great building block upon which to quickly deploy highly scalable websites.