Featured Content widget: highlights documents or discussions on a regular basis and great for the Collaborate on Documents use case.
View Blogs widget: use to highlight an executive blog post (Use: Executives)
Top Ideas widget: highlight ideas and their progress
Formatted Text widget: add text necessary for navigating a place or event to make an announcement front & center (Use: Get Connected).
Projects: great for highlighting current work being done or projects in the works for the Use: Have fewer meetings
Unanswered Questions widget: This widget would be is great for a support/customer service use case. The unanswered questions widigit lists questions from specified place that do not yet have a correct answer marked.
Ask the community widget: allows users to easily search discussions with a specific place for the Use: Work Better as a Team
HTML widget: allows users to be very flexible and create feeds from outside social networks like Twitter
*Please feel free to share additional widgets in the comments and I'd be happy to add these to the main document.