Expire User Passwords forces users to change their passwords every 30 days.
Benchmark Email Lite creates a newsletter signup form widget.
BuddyPress lets users register on your site and start creating profiles, posting messages, making connections, creating and interacting in groups and much more. It’s a social network in a box.
Share Buttons helps people share, bookmark, and email your posts and pages using any service, such as Facebook, Twitter, Google, StumbleUpon, Digg and many more.