Mac: Mountain Lion's new Notification Center pane is great for alerts, but News Notifications is a new app that lets you use it to keep up on your favourite blogs or breaking news as well. Just add a feed to the list, and new articles will appear in Notification Center, complete with a notification bubble at the top of the screen.
News Notifications will set you back $0.99 in the Mac App Store. Once installed, you can add as many feeds as you like, tell the app how many headlines to fetch at a time, and whether you want article previews displayed. After that, the app will fetch new articles, notify you when they appear, and keep them in Notification Center so you can click to read the article.
This is no replacement for Google Reader, unless you want a notification every single time one of your subscriptions posts a new article. It is, however, a great way to keep up on breaking news or a specific site that you're interested in following.
News Notifications ($0.99) [Mac App Store]