Here are some of the available add-ons to buy or download:
The Members module enables you to easily find and remove Spam member accounts from your EE2 site.
The Followers module allows you to create friend-like relationships between site members.
FeedGrab is a plugin for Expression Engine to provide it with the ability to import data from 3rd party web feeds (RSS or ATOM), such as flickr or delicious.
The XMLGrab plugin allows you to insert the contents of an XML file (or feed, or API response) into Expression Engine weblogs.