Very interested in the "internet of making things" (or project-driven, as @ataugeron iterates it here. Have been working closely on incentives around learning by doing and so far feel that these will help: 1) Recurring and consistent "prompts" (daily challenges, sure, but try to start out with some frequency you can keep up).. compare The New Yorker cartoon/caption contest; 2) Community involvement -- let other users comment and upvote, not just "best" pieces, but "most improved", "most imaginative", "most surprising" etc; 3) Let users lead: perhaps pick one of the "winners" of the above and let them post a prompt of their own and maybe even judge the standouts.