I am part of an international team working to develop the concept of a large (20 - 100 m aperture) optical/infrared telescope on the moon. Located near the lunar pole, the telescope would observe the sky overhead unhindered by atmospheric turbulence or airglow, providing a sensitivity more than 100 times greater than even that of the James Webb Space Telescope.
In a recent study sponsored by NASA, we showed that liquid-mirror technology makes such a large telescope feasible. Liquid mirrors rely on a balance between gravity and centrifugal force to produce a precise liquid surface on a light-weight support structure. On the moon, a low-temperature ionic liquid could be used, coated with a reflective layer of silver (Borra et al Nature 2007).
Our team is now developing this concept further with support from the CSA.