Find and follow other people - Google Reader now lets you find people with public shared items and subscribe to their shared items in one click. You can use the new people search feature which is powered by Google profiles or browse by name, location, or topic. Then when you find an interesting Google Reader user to follow, you may do so now easily inside Google Reader.
Share Items with Specific Group or with Multiple Groups - For those who are not into sharing items they read publicly and would rather share it with specific group of Google Reader users, you may do that now inside Google Reader. Only the users you add to your sharing groups will be able to see your shared items as well as make comment on them.
Link Items to your Google Profile - If you're using Google Profile and you want people to know what you're reading online using Google Reader, this feature will let you add a link to your shared items. Anyone using Google Reader's search feature will be able to find and follow your shared items. To activate this feature, you simply check the box that say "Add a link to my Google Profile" while inside Google Reader. In addition, you can also give your Google Reader shared items a custome URL which takes the form of your Google usersname.
"Send to" sharing features - Google Reader now lets you easily share items you like to Blogger, Twitter, Facebook and other social media sites through the "Send to" feature. You activate this feature at the "settings page".
Subscribe to feeds of people you follow - You can now subscribe to blog, photos or Twitter updates of people you follow on Google Reader provided that the people you follow has included these in their Google Profiles.
Popular Items and Recommended Sources - Two ways of finding interesting content on Google Reader from all over the Internet. Google Reader now suggest other items from the Internet not necessarily from feeds you subscribe to and presents this to you based on what the Google algorithm thinks you will like.
Personalized Ranking of Feed Items - New "magic" sorting option that reorders items based on your personal usage and overall activity in Reader instead of giving you the default chronological order. You can choose this view by clicking on "sort by magic" under your Feed settings menu.