Splashy displays a bootsplash in user space with standard debian kernels. Backports for sarge are availble at http://layer-acht.org/splashy/ because splashy is not yet in unstable, and only backports from testing go to www.backports.org.

And be warned, splashy might erase your disk or similar! :)

For more information on splashy, see the splashy wiki.