I try to replicate a blog with posts, tags for posts, and users. It's a good way to get familiar with the ORM and creating associations assuming you will use relational data. I recently started learning Play Framework (Java/Scala web framework) and it worked pretty well.
EDIT: This is assuming you are intending to learn a web framework along with the language.
EDIT: This is assuming you are intending to learn a web framework along with the language.