Image Galleries
Free plugins available from WordPress.org
NextGen Gallery
NextGEN Gallery is a full integrated Image Gallery plugin for WordPress with a slideshow option. Before I started writing the plugin I studied all the existing image and gallery plugins for WordPress. Some of them are really good and well designed, but the gap I filled was a simple administration system at the back end which can also handle multiple galleries.
Flash Gallery
Flash Gallery is the only practical way to publish VAST amount of pictures in a post. Features full screen viewing, slideshows, albums and more. The Flash Gallery plugin lets you turn your ordinary galleries into awesome image walls, with support for multiple albums per post, full screen viewing and slideshows.