Password protect pages/posts while retaining search capability of content?

[ Moved to the Fixing WordPress sub-forum. Please do not use Developing with WordPress for these topics. ]

I would like to make a WordPress site with an area only accessible via password. This area will feature a catalog of pages or posts that needs to be searchable by keyword or category or tag (preferably all three). It would also feature a couple of private forums (which would have separate passwords). What is the best method for creating this kind of site?

In setting up some test runs, I’ve noticed that making a page or post private or password protected also effectively removes the content of that page/post from any search queries on the site (via the standard search field), even when searching after using the password.

I’d like to avoid having anyone who wants to use the site to have to register a user account. I’d much prefer a simple password entry, if possible.