This is obviously very subjective because it depends on how you think the best way to help the world could be. I'm sure some may argue that typical software engineering helps the world, albeit with some degrees of separation, but I'm sure there are people out there that know of great causes that could use a software engineer.
This also makes massive sense to me: http://worrydream.com/ClimateChange/
I basically believe the future of humanity lies in collaboration. As problems increase in complexity, we increasingly need to collaborate to identify the relevant problems, understand them, formulate solutions, experiment and implement them.