AllDroid - View topic - How to *completely* get back to stock (no su, no busybox) <------- That's the link to the info below. Or you can just read it here.
How to *completely* get back to stock (no su, no busybox)
Download this: http://downloads.sholes.info/update.zip
Place it in the root of your sdcard, so /sdcard/update.zip
If you're still on the stock recovery, choose "apply sdcard:update.zip"
If you're using sprecovery, choose "install", then "Allow update.zip installation", then "Install /sdcard/update.zip (depreciated). After it's done, go back to the root menu and choose "wipe cache partition" (It's also a good idea to wipe data/factory reset also, but not necessary). Reboot when that's done, and when you reboot, you'll be completely back to stock (no su, no busybox, no nothing).
(Note: This is re-rootable, so you can always root it again if you wish)