Tons of stuff. But in the end, I believe the greatest cause for a human being to work for in our times would be to help humanity become an interplanetary species.

We do have enough problems on earth, but that will never change - at least not in time before some global catastrophe. Spreading out to other planets would not only help avoid extinction but would also provide us with new chances to set up better social environments with less social complications and require some major technological advances.