This plugin removes the admin bar completely from the public and admin areas of the website. Can be used either as a normal or MU plugin.
Upon activation/installation this works immediately. Nothing fancy, the admin bar is just not loaded anymore.
BuddyPress 1.1 Onwards
You can also add the following to your wp-config.php file and then you don’t need this plugin ( sniff ;( ) :
define( 'BP_DISABLE_ADMIN_BAR', false );
Free Download: Download this wp-plugin