I just found out that AdSense registration might be trickier that expected, when trying to login to the account I created earlier today I get the following message:
"Account Not Active
An AdSense account does not exist for this login, as your application is currently in review. Within a week of your application date, we'll review your application and follow-up with you via email. Once you are approved to join AdSense, you'll be able to log in to your account and get started."
I guess I'll have to wait and see.
Update (11:55 PM): I've just received an email saying that my AdSense account has been approved and it is already active. That was fast!