We've been having some issues with activation mails not being received - we're looking into this.
In most cases, the email is being received but being marked as spam. So if you don't get it, be sure to check your spam-folder.
I'm also activating all pending activations regulary, so if you haven't received it, you're most likely able to login an hour later.
I'm sorry for the troubles - I'm working on a final solution for it!