The nVidia 460 graphics card. $200 for the version with 768 MB RAM, $230 for the version with 1GB of RAM. It's not a 480, but for less than half the money pretty darned respectable, and by the time I can kinda sorta justify getting one, it will be even less expensive.
UPDATE: Reviews say that there's more difference than just the amount of RAM. and that one should spring the extra $30 for the 1 GB version.