Gallery2 is a PHP based photo gallery system (see http://gallery.menalto.com/) and this project contains some tools to work with the remote api via C#.
There are four items currently available:
(Tool) For people just wanting to export all their images out of Gallery2, there is g2Export which is a command line tool to export images.
(Tool) For people wanting to get information out of Gallery2 into a sane format, there is g2 Album Management which is an Excel 2007 add-in to export information about albums and images to Excel.
(API) For developers wanting to write their own tools or integrations, there is the SADev.Gallery2.Protocol which wraps the Gallery2 remote API. Please see the What you should know? page for information on using the API.