An RSS button on the profile page to subscribe to a specific user's blog or article posts would be great.
In the same vain, being able to subscribe to email notifications whenever a specific user posts a new blog entry would also be nice. Kind of like subscribing to a forum thread.
I see this as a good way to pull members together as it provides more content to the site and gives the chance for mambo/joomla to "work" with user's individual websites.
I recommend to add a RSS field to the users' profile. A separate module would would work with CB component that lists out which user's personal blog has the newest update. (This is a way that the friendster-dupe of Japan - Mixi is doing. Each member can see his/her friend's newest update on the ouside blog.)