The TwitterFeed.com site looks horribly old-school. It got bought out by bit.ly and I'm afraid they haven't put much effort into updating it. Their last blog entry was about ten months ago as I'm writing this. The deal is that you can set up an RSS feed to post to Twitter, Facebook, LinkedIn, a LinkedIn company page or app.net (?!?). The service is free, which is a kinda big deal in this day and time.
There's not too much control you have, other than how often they check your RSS feed: from every half-hour to every day, how many new posts to pull, which RSS fields to post and if they should run it through bit.ly (or some no-name competetors). Note that most of the interesting settings are under the "advanced settings" when setting up a feed.