Whenever I find myself wishing for a tool to do (whatever), I habitually add its description and distinguishing features to a list that I keep for this purpose.
Then, when I want to try a new language, I already have a list of project ideas.
Not every new language is a keeper for me, so the project I choose doesn't necessarily get finished in that language. That's okay, because the process still gives me the real-world experience to find what I like and dislike about the language. It also leads to improved design and faster development when I pick that project up again in some other language, because I'll have already explored the underlying issues.