I need a project that motivates me to do something constructive in my spare time.

I just realized that I want to drop one of my hobbies, and i need to fill the spare time with something else (other than excercise and masturbation). I need suggestions on a fun project. Bonus points for:
– Something technical/computer related (I can program, and im skilled in engineering, but i dont have a garage to work in)
– Something that’s rarely been done before or has been done but poorly.
– Something that makes people happy or does something good for people.