A recent site launch has a bit of a buzz surrounding the use of parallax backgrounds. When resizing the window width at: http://silverbackapp.com/ you will see what I mean the leaves have a very three dimensional effect. This effect would be great to use with any of the jquery scrolling plugins etc, like: http://www.learningjquery.com/2007/10/improved-animated-scrolling-script-for-same-page-links and others.
Dropping a bug in everyone's ear then, that this might be a fun idea to play around with. Here's some other links on parallax scrolling: http://en.wikipedia.org/wiki/Parallax_scrolling http://inner.geek.nz/javascript/parallax/ http://www.esqsoft.com/examples/fly_parallax/fly_parallax.htm -this ones a bit much but really illustrates the motion effect.