Gift Vouchers / Discount Coupons for RC1, RC2, RC2a
You can see a video of the system in action at http://www.clubosc.com/gift-vouchers-rc1-and-rc2.html
Download includes files to "drop in" on a new install of osCommerce. Or files so that you can add this into a modded RC1 or RC2 etc yourself.
As far as I know this is the only GV/DC contribution coded specifically for osCommerce RC releases.