My highest score on the SAT is a 2240. I got a 690 on Critical Reading, a 750 on Math, and an 800 on Writing. The schools I'm most interested in are Brown, Yale, and Columbia. Are my scores good enough, or should I retake the test?
You have a solid chance of admission with your current scores, so you don't necessarily need to retake the test. These are the average scores for each of the universities you mention:
Brown: 2155 (1495 on the new SAT)
Yale: 2265 (1545 on the new SAT)
Columbia: 2215 (1520 on the new SAT)
Yale is the only school where your score might be a little risky. If you choose to retake the SAT, you should focus your prep efforts on raising your Reading score into the 700 range.
Don't stress yourself out too much with this, though. At such an elite level, a higher SAT score isn't going to make a huge difference in your chances. Your time is probably better spent improving your application as a whole and writing a great college essay.