will tap the social aspects of popular web services such as photo sharing, blogging, and tagging, as well as sharing the user's activity with their friends. Firefox could become the place where you keep up with everything online. The main interface consists of boxes representing friends whom you select. Their faces are supposed to light up when they have something to share. More practically, you're able to sort by friends, their content, or content type. There are more specs in the The Coop's wiki
The Coop could set Firefox apart from Internet Explorer once again - IE7 delivered most of the features users liked in Firefox but were absent from IE6. It would not be surprising if Microsoft, Apple and other browser developers quickly begin to shadow the project's progress.
More details on coop could be found here.