It will run along the lines that I described previously, be quite informal and not assessed, so in many respects it's more of an uncourse, but formal recognition by my department that all students must complete the course is an important component. The completed/flunked stamp that I will be able to award makes the participants stakeholders, the absence of which scuppered Small Worlds.
Students will practice their scientific writing skills, and I'll also give them some helpful hints about (social) bookmarking sites. They'll need to join the CiteULike group I'll set up to collect some of their assignments. And they might want to ask me (and each other) for advice via Twitter. Later, if they want to continue to practice their writing, they can join the departmental blog network. In other words, Son of Small Worlds kicks off in October ;-)