I've blogged very little about my photo gallery, Kevin Martin's Open Source application Gallery Server Pro. It's very impressive, full featured and rock solid. It's a media gallery and supports much more than photos, but that's all I plan to do with it for now.
I really like how it handles .ZIPs of multiple images on upload and automatically extracts and processes the individual images. Uploading images is extremely easy and fast.
I also love the options you have with the image. I circled the "triangle" icon because it may not be obvious that it launches the slideshow, which is very sweet in that the slideshow images can be medium or large, based on the size of the image being viewed when you launch the slideshow.
Below are photos of my home town of Red Lion, PA, taken during the recent Memorial Day weekend. The album is located here. Be sure to check out the slideshow feature.