Yes, a 216 is good enough to receive a National Merit, as that is about what I got on the PSAT (though I only ended up being a semi-finalist for the actual award - still looks good on your transcript). Also, if you add a 0 to the end of your PSAT score, that is supposed to be about where you'll score on the SAT, though I don't know how accurate that really is (I received a 1960 on the SAT, should have been around a 2100 if that was true).
The SAT today consists of three sections: Math, Writing, and Critical Reading, each worth up to 800 points, unless they changed it since last year. The Writing section is fairly new, and so colleges have not been considering your score in that area when applying for scholarships. It consists of a multiple choice section and one essay. However, I believe that starting this coming spring semester that they are taking it into account, so lucky you gets to worry about it.
It's my personal opinion that the essay part of the Writing section is a little out of whack. I think that they're looking for people who follow the silly "tell them what you're going to tell them, tell them, then thell them what you told them" format, which I adamantly did not adhere to, because it's stupid. My college writing professor has said the same thing. He's also said that I'm a gifted writer, which is hilarious because I only got half credit for the essay both times I took the SAT, and failed another essay for a CLEP.
Apologies, rant over.
However, on the subject of scholarships, absolutely do not forget about your high school GPA. When being considered for non-need-based scholarships, SAT scores and your GPA are always found together (except maybe for the National Merit, I don't remember). Also, if you were homeschooled like me, expect to be excluded from a very large percentage of state-funded scholarships. I was denied a full ride scholarship I qualified for simply because I did not have an obviously arbitrary 'class rank', and was not even offered financial aid of any kind from Purdue for the same reason. But yes, if you have a good cumulative GPA (at least 3.5, preferably higher) and a good SAT score (about 1300 Math + Reading for the higher scholarships last year, but if they start including Writing I don't know), you shouldn't have too much trouble getting a good scholarship.
Oh, and Moosetek... misspelling a word doesn't affect your Critical Reading score, because they're all multiple choice - at least on the SAT. The only thing that might hurt is your essay score in the Writing section.