best way to add drop down menus to navigation bar

Hey there
Still pretty new at this but I’ve got a site running WP 2.9.2 with a modified theme where I’ve created a navigation bar. Now I have some subpages and wanted to add drop down menu functionality to the existing nav bar to allow accessing the sub-pages while retaining the styling. I have never done this so my question is what would you recommend as the easiest way to do this. I have moderate knowledge of CSS and minimal knowledge of javascript. This is the site: http://www.c-velocycling.com
thnx