Besides amateur camera-balloons, it's pretty difficult to get a viable science experiment into space. You need to buy a launch vehicle, license it, find a place to launch from, protect your payload, and get permission to actually launch, for starters. In the past, you might have partnered with NASA to do this, but it's never been easy to win federal support for a rocket or space station excursion, and it's about to get even harder after the space shuttles retire this summer.
But the transition away from the shuttle is promising for experimenters, as a new generation of privately built and operated spacecraft is poised to take over. The commercial space tourism industry will transform the way scientists study microgravity, offering lower prices and greater convenience than anything the government can provide. Scientists will no longer need to apply to NASA to do their experiments. Even better, they won't have to join the astronaut corps to get to space in person, a paradigm shift that could make cutting-edge research much more widely accessible.