[The complete archives of Robert A Heinlein are being scanned and loaded online](http://www.heinleinarchives.net/upload/).
Original manuscripts of every piece Heinlein ever wrote. I think I’m going to be spending quite a bit of time (and money – the scans aren’t free). Plus personal correspondence and other documents.
*: There Aint No Such Thing As A Free Archive. See also [TANSTAAFL](http://en.wikipedia.org/wiki/TANSTAAFL).