Forbidden Donut

I haven't used it in a very long time, but Gallery used to be pretty good:

http://gallery.menalto.com/

Have you considered just tapping into existing galleries like Flickr?

We wanted something where users had to register on our site so we can send out event info to them. using flickr or photobucket would only provide the gallery for us. unless I am mistaken?

Can't say any sort of script is coming to mind, might be time to learn PHP/JS! /tongue.gif" style="vertical-align:middle" emoid=":P" border="0" alt="tongue.gif" />

Drupal.

To elaborate on Alfy's point:

Drupal is a CMS package that has a large community that creates third party modules for things like photo galleries. Despite its antiquated code-base, it is one of the most popular CMS packages for PHP to date. If you're looking for to run a more all encompassing website, this might be a solution for you.

However, if you're really only looking to host a photo gallery, then this isn't really an ideal solution. The entire system runs on outdated, procedural spaghetti code that must all be run on every request. You're creating a ton of extra overhead on every request that really isn't necessary at all. Drupal is a CMS package who's core functionality allows it to update page content. Through other modules, you can do a lot more than that, but adding a gallery module doesn't suddenly change the fact that photo galleries are not its primary purpose. It's kind of like using Wordpress to run a non-blog website. Sure, it would work, and you'd get to utilize all of the awesome tools Wordpress has to manage your content, but it's simply not what Wordpress is intended to do.

Flickr has

user accounts (login: check)
Messaging system (mass mail: check)

<img src="...url..." />

I like Flickr but this website is even better.