I’ve stayed away from WordPress because in the past, the CMS didn’t seem to measure up to corporate or ecommerce requirements — a WordPress site always looked like a blog. I’m looking at ecommerce sites built on WordPress, and am impressed by the functionality. But what about building things like password protected membership directories? Say a school or a church wanted to be able to offer a directory to its members, so folks can call for homework assignments or to iron out who’s bringing the coffee cake to the rec hall after church on Sunday? Are there plug-ins for this? I see plug-ins for newsletters, for email subscriptions, etc.
The question breaks down into 2 parts. The first one is Christina mentioning that she's getting more impressed with the Themes and plugins that are coming available to make WordPress more of a full-fledged CMS. I totally agree and am glad she mentioned it.
The main question seems to be about creating a Membership Site for WordPress that allows you to have a password-pretected member's-only area. I've had a lot of experience with Membership sites since WordPress Landing Page is run as a membership site.
To create a membership site, I would suggest starting out with Wishlist Member (we have a Wishlist Member rebate if you are interested). Wishlist Member is an awesome paid plugin that takes care of a lot of the hard work for you. This is especially true if you want to route members through a payment process before they become a member.
Wishlist lets you do bulk emails, have different levels of access, and do a ton of other nifty things to make a WordPress-powered membership site.
If you want a free WordPress Membership Site alternative...
I don't know of a good plugin that is as full featured as Wishlist Member but WordPress does have password protection built in on a page-by-page basis. There is an excellent tutorial about making posts password protected here. Although this doesn't give you a ton of functionality, it is free, easy, and works for a lot of instances that you don't need a massive plugin to handle.
I hope that answers your question, and please feel free to ask your own question for the next 29 days.