What do I do with these things?

RSS feeds bring the content to where you are, instead of you always having to come back to the website to see what's new. Most new browsers allow you to subscribe to a RSS feed and let you see when new items exist. If you use a personal start page like iGoogle, Netvibes or My Yahoo!, you can add a RSS feed address to have new content appear there. Another option is to use a "feed reader" program to collect and display RSS feeds from around the web. This gives you a central place to keep up on sites and content that you are interested in. Examples include Google Reader and Bloglines.

You can use one feed for the specific content you are interested in, or use them all (the "New" feeds consolidate recent places and events for a location into one list). The "Today" feed will show all of the events for the current day wherever it is displayed. If you are a web developer you can use RSS feeds to display Happenstand content in web applications or on your own site.
 

Further reading

Feed 101 - a nice overview of feeds and how to use them from the Feedburner Help Center

An explanation of RSS feeds on Wikipedia