I have two photo display systems. One is on photos.spine.cx right now. It just reads directories for JPEGs and serves 'em up. It's pretty simple. The other one is almost finished development, and it can be found at http://spine.cx/~sdinn/photos/. It's database driven, which means you can add comments and the same album can be referenced from different parents. That's pretty cool, but because an album doesn't have a defined parent, you lose the "up" capability. But that's why your browser has a "back" button, right?
Anyway, tell me which one you like better.