The first thing you should do is provide a link to it from your pages so people can follow your feed.
You can also add html in the head section to help browsers and search engines find your feed:
<link rel="alternate" type="application/rss+xml"
title="My RSS Feed" href="
http://www.mywebsite.com/rss.xml" />
Then there are many websites which you can register your feed with. Some of the major ones:
http://feedburner.google.com/http://technorati.com/
