Are you looking for pass-time projects, or do you want to improve your career path?
Assuming hobbies: I'm sure you have a small blog you can create FE or BE to, if you prefer 'real world' or robotics projects you should get Arduino and Raspberry PI and play with it. You can start making your home/condo 'smarer' by integrating physical stuff to it. Try programming an 'arcade' game to a platform you like (web, iOS, Android, etc). Playing with 3D graphics is always fun, learn about 3D libraries and techniques like ray tracing and try to recreate your real world. If you prefer mathematics, read about Bayesian distributions, and this about how you'd make a better recommendation system to ranking system to a site you're using.
This is quite a difficult question without knowing you. My biggest problem is aways picking out what to do with my non-existent free time :)
Most important -- find something that you really like doing and care about, or you'll abandon it quickly.
Good luck, and enjoy!
What do "FE" and "BE" mean?
If you mention what area interest you (mobile / web / data etc) I might know a couple more projects to recommend
(disclaimer - I maintain the site).
There are plenty of side projects that people are either selling or seeking a co-founder for. Would love to have you check it out.