Gallery is a free, open source photo sharing web application which is a bit like saying a Ferrari Enzo is just another car. Gallery 2 pretty much lets the user set up a photo gallery from as simple as a couple pages of photos to as complex as dozen of albums and sub-albums, with dynamic keyword-based albums and other features thrown in for fun. It has options for password protected albums, RSS feeds, a commenting system, etc. There’s no feature I can think of that I really wanted that wasn’t already part of the core system or easily added on through a plugin.
Like WordPress, Gallery benefits from an active community of plugin developers who have extended the features of the software. One of the nicer features for WordPress users is the WPG2 plugin which integrates Gallery with WordPress so, for example, my Gallery pages use the same theme as my WordPress blog and appear to be simply pages under WordPress. Additionally, individual images can be easily inserted into WordPress pages or posts using a special WPG tag.
If you’ve got your own server, Gallery is a cheap and highly flexible way to host a medium to large photo site.