Very deep 21cm HI observations with the GBT have discovered a group of clouds that lie between the galaxies M31 and M33 but do not appear to be directly connected to either system. These are the most recent (and most puzzling) of a population of large gas clouds without a stellar counterpart that are found around the galaxies of the Local Group. I will discuss the properties and possible origins of this material and its implication for the evolution of M31 and the Milky Way. In addition, I'll give a brief review of some other recent discoveries made with the GBT.