I have looking for free gallery for my project, I founded dfGallery and I have used it… it cool nice simple.
Created and Shared by dezinerfolio.com, with an amazing theme engine built to support custom themes with multiple skins for each. The administration console built on CodeIginter lets you manage multiple galleries and albums of different types.
You download it at dezinerfolio.com

Full Feature List

  • Embed the Gallery anywhere [Blog, Facebook, Myspace…]
  • Themes – Change the layout and the presentation of the gallery [advanced]
  • Skins – Simply edit a PNG file to change the whole look if your gallery [Skin guide in the package]
  • Flickr – Gets every Flickr album of any user [api key customizable]
  • Picasa – Load any picasa album by just configuring the URL
  • Custom Albums
  • Full control over the system from the Administration Console.
  • AJAX & Multiple Image Uploads
  • Customize the background music of the gallery
  • Fullscreen feature lets you view images with the highest resolution.
  • Built on Flex 3 SDK
  • More coming in the upcoming builds…