Jet Packs - Everyone has been hearing about jet packs ever since the 1920's. They were mostly used by astronauts in science fiction tales, even the U.S. Army tried to create one to be used in the military. At the moment, only water powered jet packs are available that can only send people hovering at around 30 feet.
Flying Cars - This has been on people's minds longer than jet packs. The idea for flying cars has been speculated for over 100 years, ever since the first car was invented. A few people have tried to make one, but due to safety and practicality, it hasn't been possible yet. There is a hybrid flying car being developed by Terrafugia that will have a distance of around 500 miles. With any luck, this may be available to purchase by 2015, but chances are it will be expensive.
Elon Musk's Hyperloop - Tesla owner Elon Musk is looking at changing the way commuters transport. Almost like a futuristic train, this sends commuters located in little pods through a giant tube to wherever their destination is. At speeds of around 598 mph, this could bring people from Los Angelis to San Francisco in around 35 minutes. There has yet to be a definite date as to whether this will be built or not.
Hoverboards - First seen in Back to the Future Part 2, this is basically a skateboard that hovers over the ground with no wheels. Almost like a segway, you move the hoverboard by moving your body in a certain direction. There have been a few attempts at creating hoverboards, but the results have either been fake or unsuccessful.
Time Machines - Time travel first started in the 1890's with H.G. Wells novel The Time Machine. It would be fun to travel to any time period and see historical events as they happen or what may happen in the future. Many theories have been developed over the years as to whether time travel is possible. While some theories have suggested ways of traveling backwards in time, including traveling faster than the speed of light or through wormholes, there haven't been any theories that could explain how people could travel forwards in time. Since there has been no real evidence of people seen in old photos that have visited the past, chances are it's either impossible or it will take a long time to discover the way or ways to travel through time.