If you haven't found it yet, I'd encourage you to check out the awesome new open-source online encyclopedia called Wikipedia.
The name comes from the web page concept known as a 'wiki', whereby any person can change what's shown on the site.
Basically this is an online encyclopedia that you can contribute to. If you know more than is in an entry, log in and edit it.
The site has become massive, and thus, very useful.
There's lots of room to explore. I could spend hours jumping from page to page.
There's lots cool you can find, and the best part is you can add to it if something is lacking. Say for instance, you want to contribute to Chicago's entry, you can do so here.