JavaScript in the browser allows for quick feedback loops that I think can be rewarding for beginners.
Help them come up with projects that they're interested in and will challenge them a bit, but are also tractable. Beginners won't have the context to be able to scope a project out, or to decide what is realistic and feasible, either. I find that can be a roadblock for people who are just starting out, where they learn the basics but can't figure out what to do with them.