Until version 3.0, there was WordPress, and then there was WordPress MU. WordPress itself could create only one site, while the MU (multi-user) fork could be used to create a network of related sites similar to
edublogs.com. With version 3.0, the two projects have merged once again. When you downloaded WordPress, you gained all the features that used to be specific to MU; they're just hidden until you turn them on.
Even if you don't need to create a whole network of user sites, you could use the network features to manage multiple sites rather than installing WordPress separately for each one. This would be especially useful if your group of sites shares the same pool of users, since they would ...