Hi

I'm considering using XOOPS for a website for local Humane Society organizations in my area. The Humane Society is a non-profit no-kill shelter that takes in animals and finds them homes, has fundraisers, adoption clinics and of course lots of dogs. Any suggestions on how to get started would be appreciated.

Hmmm,

Check out http://www.freeformsolutions.ca

Starting a New XOOPS Site provides the basics and Christian XOOPS Resources has a bit more about strategies and methods.

What specific content/functionality are you looking to provide?

By defining what you want to show to the world and what kind of interactivity you want with the users (= what the users can do with your site). Then select the appropriate modules from the module repository. The module packs give an example how different module configurations can target a websites purpose. Then select a theme to have the looks that fit your house style.
You may have also a look on the presentation of or links to some existing XOOPS sites. Check out their functions. The URL can indentify the module used, and when in doubt, ask here or the webmaster of the site which modules they use.