I have been adding some additions to WordPress to lock it down a bit and keep regular users away from wp-admin. There is a bunch of stuff out there to do this type of thing but I found the best combination to upgrade your register/login system and to keep the average user away from wp-admin so they stay on the site was to use Register Plus and WP Block Admin. They both serve different purposes but combined together they provide a much nicer user experience.
Register Plus: This WordPress plugin will allow you to create custom emails to users, a custom registration form, a password strength meter, a captcha, user registration verification emails, and more. When creating the custom registration form you can add custom fields, add custom CSS, etc. All in all in provides complete customization of the registration form and process.