I recently used PuppyDog and Bravenet’s password protect service. Bravenet was good, but it didn’t have the feature of member sign up form. Is there any other such service which would give this feature as well as the one by Bravenet?
Try using accessprotect.com . The downside to this is that it uses url hiding so you can see the real website address.
If your webhost uses Cpanel, there is a option in there called "Password protect directories" This allows you set setup your own password on a folder in your website.
It all depends on your ability to code and/or edit code. There are plenty of free PHP scripts along with tutorials that you can edit to better suit your requirements. Take a look at http://www.plus2net.com/php_tutorial/php_login_script.php