The Login Redirect and Logout Redirect plugins are like salt and pepper shakers. Usually when you log in to WordPress, you’ll be sent directly to the dashboard. The Login Redirect plugin lets you specify the URL for redirection after users log in, just as you might imagine. The Logout Redirect plugin lets you set a custom URL for automatic redirection after users log out.
Download both of the plugins for free today from WPMU Dev.
To get a wiki up and running you used to need to install Mediawiki and toil away for days configuring it... not any more! This plugin gives you *all* the functionality you want from a wiki, in WordPress!!!