If you are a RSS user, not just to read blogs, instead almost every syndicated content, you will be using any kind of RSS aggregator. This kind of software software uses to be known as "readers".
One of the oldest sites that provides this functionality has been http://www.bloglines.com since then, almost every portal has included a way to read RSS feeds from the "MyPage" page. But we need more functionality, we need to track the items you have read, organize in categories your feeds and much more.
The on-line giants (Google, Yahoo and Microsoft) have released their own versions.
http://www.google.com/ig allows you to read feeds along with your gmail account, and search history
Another more specialized is http://www.google.com/reader