Please don't fall into the trap of believing that your daily work and working for the greater good are mutually exclusive.

You may not realize it, but you are often contributing to the greater good on a daily basis simply by doing your job. It's sometimes hard to visualize this because we are often many degrees of separation away from the "end user".

You don't actually have to be physically building that home for the homeless or providing food for the hungry; the work you're already doing may be helping someone to help someone else to do that.

I've even thought that the best way to put your technical skills to the greater good is through your day job, not instead of it.

Some of my days jobs have been to write software to ensure that:

  - people get the right prescription medication on time
  - firetrucks and ambulances get to where they're supposed to be
  - parts that go into cars and planes are properly certified
  - prisoners are kept in jail
  - those same prisoners get proper medical care
  - electronic equipment gets assembled properly and on time
  - medical supplies get dispatched to where they're supposed to
  - insurance claims are processed properly
  - quality data is properly maintained for food items
  

You don't need to do charity work on the side in order to contribute to the greater good.

On the other hand, if you don't think that the work you do during the day contributes to the greater good, then maybe you should consider doing something else with your valuable time.

Do good and get paid. You can do both at the same time.