CSS Drop-down menu
Yeah, I know there are a lot of CSS menus out there, but this one has to be one of the best. It’s easy to customize and you can change the transformations to horizontal, vertical left-to-right, vertical right-to-left, horizontal linear, and horizontal upwards. Looking at the CSS code it seems to be very well written and documented. Theming the menu is easy, so adding it to your site is a cinch. I have a feeling I’ll be using this drop-down menu framework in the near future.
Free under the GNU General Public License