Not sure why this is getting down voted. Software engineers have high earning potential and can have more impact by donating part of their salary instead of volunteering or doing non-profit work. Plus, software seems to be a good industry to be in for getting a shot at making ridiculous amounts of money which can eventually be donated (e.g. Bill Gates).

This is indeed a boring answer but a realistic one, especially given how vague "an actual impact on the world" is.