Coppermine Photo Gallery is a great free software, the best photo gallery I could find when I was trying to add dynamic content to this site; unfortunately it didn't have some features I wanted and had way more than I needed. So here's my modified version, of course GPLed:
cpg-modified-20050207.tar.bz2
Warning: I do not provide any support, any installation, configuration and use instructions; it is provided as is.