TwitterFeed is a web service that lets you push RSS feeds to Twitter for easy promotion of blog posts, etc.

Twiffid shows you the headlines of the websites your Twitter friends have listed in their profiles. See what your Twitter friends are blogging about!

Twaitter is a suite of tools to turn your Twitter account into a full-fledged business interface. Features include: scheduling, recurring tweets, translation, feeds, scheduling en masse, etc.

Stammy Script: RSS to Twitter using PHP is a PHP script that lets you send your RSS feeds to Twitter.

Gwibber is an open source microblogging client for GNOME developed with Python and GTK. It supports Twitter, Jaiku, Identi.ca, Facebook, Flickr, Digg, and RSS.

Flock O'Tweets lets you group your followers into contextual, easily-digestible RSS chunks.

FlashTweet is a Twitter application that simplifies the process of acquiring more targeted followers. You can add multiple Twitter accounts to your profile, discover who you are following that is following you back, mass follow users based on search terms and location, unfollow multiple friends at once, schedule tweets in advance to run throughout the week, insert RSS feeds that will automatically tweet the title and link of your blog or another site.

Feedly is a Firefox extension that draws together favorite content, including Twitter, into a fun, magazine-like start page that promises to change the way you find your news.

FeedTweeter is a service that posts your RSS feeds to Twitter. FeedTweeter is capable of drawing on RSS feeds from several sources (like Plurk and Identi.ca).