MySlimbox
Lokesh Dhakar's Lightbox2 is really cool, I use it for mulpo.com and many others websites.
When I showed the Lightbox2 to some clients, they asked me if the overlay could be lighter so that you could still see the content of the page you were browsing. They also asked me if the buttons could always be visible and to go on top along with the data container.
When I was changing the layout of the Lightbox I found Slimbox, which is a clone of Lightbox, but it is much lighter and the animations are smoother. It was also much easier to modify the layout of the Slimbox than the Lightbox. This is only a variation of already brilliant code originally made by Lokesh and then modified to work with mootools instead of prototype by Cristophe Beyls.
You can download all the files going to my post at mulpo.com
If you want the original Lightbox2 go to Lokesh's site
If you want the original Slimbox go to Cristophe's site