This plugin lets you show a "map" of the cities your users are located in (also shows the number of users per city, if more than one). This is a great "feature" for your site, as it shows the broadness of your user-base is.
This plugin lets any of your users setup their entirely separate WordPress Blog! This is a great incentive for users to actually signup to your site (and almost a "selling point" - as lots of people want a free blog where they can share stuff =)). VERY simple to setup, and very easy for users (even your current ones), to setup their own blog.
This plugin is a port of our popular "ContactPage" for LinksSQL. Boasting the similar features, this plugin makes a great addition to anyones site. Even if you only want to use it as an integrated contact form for yourselves.
This plugin lets you link to a .cgi script, so people can view the users "profile". On this page, you can display any of the information from your comm_users table. For example, <%comm_username%>, <%prof_gender%>, etc.