Is it appropriate to contact professors after application submission?
After reading some of the other reponses to your questions, I feel I need to give you fair warning that we receive tons of these emails, many of them obviously scripted (e.g., my name is in different font, the area described is irrelevant to me, for female faculty the email starts with "Dear Sir," etc.) My default reaction is to delete. Mind you, this is not to say your email would be like this, I'm just letting you know what you're up against.

The only emails that I try to pay attention to are of two types:

1) There's something obviously strong about you by just quickly scanning your email: You are an undergraduate student from a top school, or your grades are super-strong, or you've done some interesting research, or it's obvious that you've read some paper of mine and have legitimate comments about it.

2) Your subject line reads: "Undeterred prospective student." This is actually at the bottom of my info page for prospective students, which is linked to prominently on my home page. The vast majority of email requests I receive is from students that didn't bother to read it, so when I get an email with that subject I make a point of looking at it.

This is irrespective of when I receive your email; in fact, one could argue that the closer to the review period, the better.