Astronomers have created the largest earth-bound telescope ever by connecting a series of radio telescopes across the globe together. By using Very Long Baseline Interferometry they are able to essentially correct each other's view to produce resolutions 3,000 times finer than the Hubble telescope which orbits the Earth.
These techniques used with terrestrial telescopes allows us to create 'virtual telescopes' as big as the entire planet. However, scientists are planning on launching groups of satellites that will create virtual telescopes that are millions of miles across in space. Astronomy is soooo cool.