I love Google Reader, there is not a single day without using it. You can keep up-to-date with hundreds of feeds, categorize them, read them all at the same time when you're procrastinating too much (press shift+A), and much more. Definitively, one one my favourite web app !

I forgot to say that you can easily share blog posts with friends, and the new feature is that you can now also annotate these shared items !

The second feature, though less useful, is the nice picture that you can choose to add on top of your shared items page. These days I'm really into fishes so this picture really suit me presently (more on the fishes very soon).