[txutxu]

Option A) You can port any thing you have written previously in other languages. Take something from ~/src/ that way you know how it works and you will focus in learn the language.

Option B) You can think about something you're passionate in real life. Code something about it. Does not need to "solve a problem", maybe simply try to improve something that already exist and you love. That way, maybe your state will be positive and the learn experience, better.

Option C) Try to automate and improve your workflow in the new language.

If in any case you need an idea... "a blog engine".

Update: added option "C" and an idea as requested.