BuddyPress.org

Tested it once, BP Template Pack activated does include the basic CSS necessary to style the different core components – http://svn.wp-plugins.org/bp-template-pack/trunk/bp.css

You could customize template pack’s css in your WP theme’s style.css to match say, link or background colors to match your theme

Btw, check the source view of your BP-enabled pages and see if the link to the bp.css from template pack is rendered there, it should be.