A "To Do List"
How cool would it be to have a "to do" list on here? I love the favorites feature, and agree with other posters that it needs to have a way to easily organize your favorites or search within your favorites. (I'm not sure about all it has, can't afford a pro membership yet)
But, for those with pro, I could see how a to-do list would be sweet, where you can add an instructable to your "to-do" list and go back later and prioritize the items within it. Kinda like how Amazon has the priority wish lists.