For email activation, just include an activation link in the email it sends out to activate, where someone can just click on it to activate instead of having to fill out a form. Unless there's some reason why you're not handling it like every other board does.
Also, on the screen where you enter your username and activation number, put the "Resend Activation Key" button below the "SUBMIT" button. Also make the submit button more prominent, and the resend button to look more like an emergency option.
Right now, with the Resend button right underneath the two form fields, I can see a lot of people accidentally clicking that instead of submit.
With so much competition these days in forum software, it's these little things that matter as much as the big things.
Also, new line and spaces don't seem to be working when I typed this post. I had to edit it to add spaces between lines.