What projects do you think one should embark upon after learning a new technology/programming language in order to improve?

Answer 1

It would be different depending on the person. If you've got a good amount of experience, you'll be able to do more with a new language/tool than if you are a beginner.

Rule of thumb: Look for something mildly challenging.

You should have an idea about how to to solve the task, but it should still require some effort of researching, thinking, debugging.

If you have to struggle for days for a few lines of code - too hard for you. If you basically just have to write it down - too easy.

Answer 2

You could look at codingame.com to improve your coding abilities, perhaps.