Almost all cards that are available right now are SM 3.0 capable.
Do you mean you want to magically make your Nvidia 5900 or ATI x800 support SM3 without having to spend any money at all? Not going to happen. What do you have and what are you trying to do? Give us some details, not an empty quote box.
This next topics has been merged by Mousemonkey K so i need a shader model 3 with no cost suggestions