It depends on your level of talent. If you are a legitimate D-1 player -- a player who has a real chance to contribute at a BCS school (Pac 10, ACC, SEC), then a great number for all but a few schools is 1000 (math, critical reading) or 1500 if you want to throw in the writing. This goes along with a GPA of between 2.6 and 3.0. And what I mean by that, is that you are definitely in with those results.
At Stanford, increase the SAT to 550 in all three categories (or 1100 for the two)and the GPA to 3.0 and you are in -- if they like you enough on the field. The ACT provides additional opportunity.
If, however, you are not a player who clearly can help these schools on the field, the requirements are much, much higher.