Quick gallery
Quick Gallery is very simple and free. No MySQL. Just put your images in image directory and that's all. QG automatically creates thumbnails. In a config file. You can set number of images per page, width and height of small and big images. Images sorting. You can choose one from five skins.

An easy-to-use image gallery that looks like a slide album. All thumbnails will be framed with a slide mount.
Features:
- Auto indexing of directories.
- Auto page generation.
- Auto framing of thumbnails with orientation detection.
- Thumbnails generation.
- 1/2, 1/4 size display.
- Auto closing of popup window.
- Requirements: php 4.06 or later, GD library optional; Photoshop 6.0 for editing the slide mount images.