There are a lot of easy ways to get a free site on to the Web right now, from MySpace (not a bad solution if you want to advertise your group to 40 trillion teenagers) to Wiki services like Wetpaint, but Nexo's focus on group dynamics pays off. The site is a good option if what you need is to keep a group of people informed and in touch with each other.
Once you set up the framework for your group site by adding elements like a home page, a calendar, and a forum, you can then invite people in your group to participate and contribute to the site.
It sounds humdrum, but Nexo has a good blend of structure and openness. For example, it's easy to set up a simple-to-use photo page, and it's also simple for anybody in the group (who has permission) to add to it, either by uploading their own pictures or by pointing to their Flickr images. Videos work in a similar way.
There are nice little Web 2.0 touches in Nexo that delighted me when I tried the service. Two examples: First, comments or journal entries that people leave on a page are updated in real-time for all to see; you don't have to reload a page. Second, the photo upload tools gives you a quick zoom-and-crop option when you add pictures. It's a little thing, but it makes adding a portrait to your profile page much easier.
If you want to set up a family site, you might want to use Vox, which is based on a blogging platform. But anyone who works with a group or club that could use its own Web site would be wise to check out Nexo.