Google Talk gives you desktop alerts whenever you receive a new email and while you wouldn’t want your RSS feeds to pop-up on your desktop all the time (which is why you get them in Google Reader and not in your mail) you might need a desktop notification for an RSS feed you’re actively monitoring. RSS Alert is a chrome extension that lets you add feeds you actively want to monitor and gives you desktop alerts whenever there is anything new on the site.
When clicked, the story/article/news item is opened in your default browser. The alerts don’t go away like the email alerts from Gtalk, you either have to close them or click them to make the pop-up go away. The extension does not monitor the feeds you’ve added to Google Reader, you have to add the feeds yourself by clicking on the extension icon next to Omnibar.