Twitter's new Lists feature has rolled out in beta to a large number of users, and it adds a lot to the Twitter experience without detracting too much from the site's simplicity. You can create, view and manage lists of users from the Twitter.com sidebar, and add users by going to your "following" page. Once you've got a list created, clicking on it will show you a timeline of tweets from the users you've added.

If you make a list public, you can send a link to others to share it, and they can add everyone on your list in one fell swoop. You can also see which lists you've been added to by clicking on a link located at the top of the sidebar next to your following/followers numbers. This bumps the link to your timeline, showing your total number of tweets, out of the way to a small-print link under your username. Of course, it's also possible to make private lists, in case you want to group people into categories without offending anybody.