I feel that the world really just needs a fresh start.
The logistics of this would be difficult, but let's dream for a bit, shall we?
Israel and Palestine: Set aside enough land (take a little bit away from the surrounding countries that don't really use all of their land anyhow) and give each equal and sufficient space to live together.
The Middle East: (Remember, we're assuming this is a fresh start) Wipe away all current and past grudges, fundamentalism and the likes, and work together towards a common goal.
Petrolium, Gasoline, crude oil, whatever you call it: Although I would prefer vehicles that did not use these, there is still a need for these, so perhaps organizing a global treaty to eliminate certain byproducts such as MTBE and other chemicals that harm the environment.
The United Nations: Implement a system that actually works. All governments and nations would be represented equally under this system. I don't know how I would go about reforming the UN, but possibly having each country pay a tax that goes towards the UN whereby giving them funds to keep the peace (sort of a global peacekeeping army for when needed) and other programs.
Research and Development: Focus this on treating known diseases, space exploration, etc, etc.
Work towards eliminating world hunger and so much more.
These are all just dreams - They all would have real obsticles if they were truly attempted to be implemented or carried out, I realize that. It would be quite interesting to see what the world could be if we all just started over with a clean slate.