Most websites prominently feature "sign up" areas, which are awesome for new users... what about the website's most frequent users? I.e. people with accounts?
I often find myself hunting for these "sign in" areas, which are small and all over the page, usually a small link in the top-right corner, too small for my fingertips, while the "sign up" are huge and in the middle of the screen.
Login should be prominent and Sign up less so! Is most of your business from the existing users or from attracting new users? Please demote the sign-up.
Or, even better: both - see how login is done for http://www.racerkidz.com - if you enter the password twice, you indicate that you wish to register. If you enter it just once, then you indicate you're an existing user trying to login.
This is R&D eh? Let me know if it makes sense or you find it hard to use...