FeedInvader is an experimental add-on for Firefox that integrates an RSS feed into your browser.
FeedInvader adds two things to Firefox. The first is a toolbar which had a range of controls on it, including a Feed Reader button, which is the second addition. The Feed Reader looks like most readers, with a list of your subscribed feeds on the left, and two more panes, one with the list of headlines, and another for reading selected stories.
You have to sign up to FeedInvader to start, and then you can build your feed library. There is an RSS button in the toolbar, which will add any page's feed to your FeedInvader account. These feeds can be viewed in the traditional style reader, and will rotate in the toolbar, giving you a constant stream of stories.
Apart from the RSS ticker in the toolbar, FeedInvader doesn't add a great deal to Firefox, which already had an RSS button, and can be used easily with a Google account. There's nothing easier about FeedInvader, and it has the disadvantage of the additional toolbar, which takes up valuable browsing real estate. Tickers can be good, but this one goes through your feeds, instead of popping up stories as they happen. In this way, it doesn't help you keep up with stories as they happen, which is what a ticker should do.
FeedInvader adds an effective and attractive RSS reader to Firefox, but its toolbar is invasive, and as a whole it's less comfortable than other RSS readers.