Some of the features coming up in Spring 12:
1. Chatter Bookmarks, allowing you to bookmark your favorite, most useful Chatter posts
2. Chatter Favorites. Search for a specific string and save that Chatter search as a favorite.
3. Chatter Influence, which allows you to find the most influential people in your org.
4. Chatter Messenger is the GTalk, AIM, MS Communicator of Salesforce, allowing you to instantly communicate with anyone in your Salesforce organization.
5. Chatter v2.0 will be released in Spring 2012 for the iPad, bringing an all new UI that is easier to use.
6. Chatter Smart Search, bringing the most important items to the top and intelligently categorizing them.
7. Data.com is making it a lot easier to search for the exact types of contacts and leads that you would like to target with advanced Google-like filters.
8. Cross object workflows
9. Drag and drop schema builder
10. Siteforce is making the publishing of dynamic data a lot easier with some of their new features.
11. Siteforce Web to Object, Siteforce will allow out of the box building of externally facing web forms.
12. Radian6, the social monitoring package, is releasing new features that tie in with the Service Cloud to allow monitoring and tracking of Cases generated from the social networks.
13. Salesforce Analytics Edition, which is focusing more on the BI crowd.
14. Email to Case functionality has now been built into the Outlook Edition tool.
15. Salesforce Mobile for Android
16. Shared Tasks are an interesting new feature, but seem very useful, e.g. Send Holiday card to all Florida contacts. Why create 100 tasks when you can create 1.
17. Social Accounts, person accounts, and social leads are now available, just like the already existing Social Contacts.
18. Chatter Answers, the enabling of social self-service. Answers can come from knowledge articles, customer service agents, and a community of experts.
Of course, more on Release note