Andrew Berg has created a nice looking, open source flash gallery named Flash Photo Browser.
Flash Photo Browser is used by uploading thumbnails and the original images in the related folders with same names and after that, the application lets you browse the images with a nice effect.

It uses the Flash tweening prototypes, blurred rect prototype, draw rect prototype and requires PHP to run.
Besides the standard look, you can also switch to the thumbnail view with a click.
Requirements: PHP, Flash Player 7+
photoDiary, is a flash web application which lets users to create photo blogs.
Blog owners can upload new photos through an administrator interface easily. Maybe, the most attractive feature of photoDiary is the commenting system. Visitors can leave their comments with a post-it like virtual-papers on any part of the photo.

Visitors can navigate through the photos with the back & forward feature, remove all comments with 1 click or send an e-mail to the blog owner.
P.S. There is an English version besides the original Italian version in the product website.
Requirements: MySQL, PHP (GD library enabled)