If you haven't received your account activation email, the two most likely reasons are:
(1) Your email client has put the email in your spam folder, or
(2) You gave us the wrong email address during account sign up.
Here's a little trouble-shooting guide to help find the problem:
(1) Check your spam folder for an email with the subject "confirm your email address."
(2) If the email isn't in your spam folder, check to see if you entered the wrong email address by trying to create a new account with the email address you think you used before.
If you used this address before, the system will let you know there's an account under this email already and won't create the new account for you. If this is the case, try waiting for a while and check your email again.
If it does let you create the new account, then you entered the wrong email before and you should get an activation email for the new account.
(3) If all the steps above fail, contact customer support.