RSS feeds can help readers follow your writings easily using a feed reader. You can ping a number of feed aggregators, some which can actually bring some visitors as well. And finally some of these aggregator service generate backlinks which can help your rankings.
RSS feeds is the best method to let your feed reader know the update status on your website. It can help you to keep contact with your reader and get the traffic
i wrote an article on this topic few days ago and you might like to take a look at it http://seoforblogging.blogspot.com/2008/08/importance-of-getting-rss-feed-email.html basically, rss allows you to spread your content to other customized sites like iGoogle, My Yahoo! etc. If people like your content then they can put your rss feed on those pages and thus become regular readers.