Google Reader now sorts your feeds "by magic"
In the sidebar, you'll notice a new "recommended sources" list. These are sites Google Reader thinks you'll like, based on your browsing habits -- if you've opted-in to let Google track those -- and your reading habits in Reader itself. You'll also see a Popular Items section from around the web, showing you some well-read and potentially relevant posts from sites you're not subscribed to.
In addition to these ways of finding new feeds to read, Google Reader can now sort your existing items "by magic," bringing the most relevant articles to the top of your list. To make this happen, go to the settings dropdown for one of your feeds or folders and choose "sort by magic." The magic is actually an algorithm that takes into account what you read and share in Reader, and it seems to work pretty well. I'm not a frequent Google Reader user, and even my relatively untrained recommendations were interesting. If you share and like items on a regular basis, yours will likely be even better.