I would create a commercially viable, extremely useful version (versus just plastic doodads) of the self-replicating fabricator ( http://reprap.org ), design a decent computer & solar cell that could be easily manufactured by this fabricator and is easy to make into a cluster system (and have semi decent performance). And create some fabrication programs that can manufacture buildings, farming equipment and other such essentials.

Then I would fund a bunch of funding into cures for third world evils like malaria and such.