Requirement to password protect areas of the blog

I am testing the suitability of WordPress for a user group with over 300 members and they have asked that certain areas of the Blog be password protected.

Their old site had a general area accessible to everyone then a members area and a Board members area, both protected by htaccess.

I showed them WordPress and they are very keen to use it but still want to maintain the structure of the old site.

The only area that really needs a Blog is the members area. The Board members and general area could be run with static pages as they don’t change that often, but for the sake of simplicity, I would like to run the entire site using WordPress, but have different areas accessible using different passwords.

Is this possible and how should I go about it? I have had a search and so far it seems that WordPress Mu is the only solution available.

thanks.