Customized site login?

I am trying to create a custom login page for my site based on the twentyeleven theme. I need for one section of my site to be password protected and available only to members of the organization. Essentially, I need a login page that will reference a database of approved usernames and passwords. Any idea how I can accomplish this?

I cannot post the site because it is currently hosted locally on my personal computer.

Thanks in advance,
Kj