Publisher?
Run a blog or another publishing business? Create a Sup channel to let Sup users keep track of your publishings. Each time you publish something, simultaneously send out a broadcast to all Sup users with a link to it! It's gets better. You can use the Channels API on Sup to configure automatic broadcasts each time you publish something.
Login
You need to be on Sup to be able to log in. To create an account download Sup and register.
Developer?
Sign in here, and create a channel. Then come up with a cool idea like "Joke for the day" and create a channel to publish broadcasts to Sup's users with whatever cool functionality you've just come up with. Use the API to automate stuff!