Just found this at the forums on the t-mobile site, its for the vibrant but i just installed it on my euro sgs and it works fine! heres the link i got from fredthemole
its a link with instructions telling you to search the market for desk home samsung vibrant.
you need market enabler to select t mobile as your carrier cause i couldnt find it using my optus(aus) one.
just searched for car home and its there too!
edit again: found a clock apk from the nexus one i think, that works on ours bar the music button, and as said in the thread i'm about to link, use tasker to create scripts to turn it on and off when you plug charger in, its great!