JV2 Quick Gallery
Simple to use gallery which is quick to install... all you do is drop the index.php in your gallery folder where your images are. Supports multiple levels, includes css styles and graphics as well as JS overlay to view the images - all in one file. Automatic thumbnails, cropped or normal. Albums can have an auto thumb of several images. Also included is an admin area which you can use to add titles and captions to photos. You can also let the titles be created from the file names. Has multiple layouts and themes. Check out several demos through the site.