They are per-forum or per-user. When in a forum category, the button will be on the upper right.
To get an RSS feed of posts from an individual user, go to their profile and the icon will be next to their name.
//edit: and, screw the Wiki until further notice. I'll take a look at system requirements again, but adding more server load to the VPS to add a second database... we'd have to have alot of people interested. (which first requires having a lot of people).
//edit 2: Gallery going up tomorrow morning. As in, this morning.
RSS is a fairly old one. It's called "Really Simple Syndication."
If you subscribe to one, you can look up (in this case) the last 15 threads made on whichever forum or by whichever person you choose. It won't show private forums. All it shows is the title, some intro text, and a link.
A lot of news serviced will have RSS feeds as well (again, just title, intro, and link). That's what it's founded for, and people who read a *ton* of news or blogs will get RSS feeds on their browsers. It's very easy to do.
RSS also allows other web forums and sites to update information from here as well. vBulletin can automatically read these feeds and post new topics. For instance, our old forums read off news from most of the top news organizations (CNN, BBC, FOX, Reuters, etc). It created these in a separate forum just like normal threads, and did it every time there was an update.
Which is the intended target. Anyone running forums on their own website that wants to see whats getting posted here can (say a Warrior sub-forum on a guild website). Also, anyone who runs personal feeds can do the same.
//edit: What I would suggest is just clicking the button in the Warrior forums. If your browser automatically supports it, it'll show you exactly what it's doing.