The next few days should be pretty exciting for advocates of space exploration. SpaceX's launch window for their 3rd Falcon 1 launch starts tomorrow (Aug. 1) and ends on the 5th. If this launch is successful, it will be the first time SpaceX has successfully put a payload into orbit aboard its low-cost Falcon 1 rocket, potentially ushering in a new era of less-costly space launches.
Not only that, the rocket will be delivering several payloads to orbit, but one of the most exciting (for space exploration advocates) is NASA's NanoSail-D, a 100-square foot solar sail created by NASA in just six months. Solar sails are an exciting technology, because they could allow spacecraft to accelerate without the need for on-board fuel, which greatly increases the costs. Also, fuel is the number one limiting factor in space travel, because the more fuel a spacecraft carries, the more mass it has, and the more mass it has, the more fuel it takes to move it. Every kilogram of fuel added provides less total thrust than the kilogram before it, so a system that can reduce or eliminate the amount of fuel needed could allow spacecraft to function further and longer.
Wikipedia has a pretty good page about solar sails.
I'm curious as to how well the NanoSail-D experiment will work, as Falcon 1 is not designed to lift payloads into high orbits. Lower orbits have increased drag, which is especially bad for solar sails given their surface area and the limited amount of pressure they receive from the solar wind.
You can watch the launch by going to the SpaceX website.