Some of George R.R. Martin's personal papers and items have made their way to the Texas A&M archive, where they are being stored for future study. This is traditional in the publishing world for well-known authors, with J.R.R. Tolkien's papers residing at Marquette University in Milwaukee, Wisconsin.
Via Winter is Coming, a few images from the collection have appeared on Tumblr. Most interesting is the above map of the lands beyond the Wall, from A Song of Ice and Fire. Presumably this is one of GRRM's original hand-drawn maps (or a copy of one), which the versions in the books were replicated from by professional artists. Interesting stuff.