Somewhere between a full blown community portal and blogging is a small niche -- multi-user blogging.

The idea is that you run a site and allow each member to have their own blog, and it's all connected under one content management system.

If this sounds interesting, and you're looking for software to do it, you might want to check out WordPress MU, (the MU stands for Multi User).

If you're looking to have more features and want everything controlled under a single unified login / user management model, take a look at "BuddyPress", (still in BETA, but looks promising).

BuddyPress is an extension for WordPress MU that adds most of the common social media functionality -- "friending", media galleries, user-to-user messaging, chat, forums, user activity streams and more.

If the software is anything like WordPress in reagrds to being easy to install, easy to configure, and attracts even some of the legions of plug-in, widget and theme developers that make WordPress better than most other blogging software, then BuddyPress is sure to be a hit.