Removed the numbers from the Keeper map on page 186 for use as a player handout.
One of the big inspiration for At the Mountains of Madness was Admiral Byrd's first Antarctic expedition from 1928 to 1930, from which Lovecraft drew many details that he would transplant onto the Miskatonic University Expedition. Byrd wrote a 100-page piece for National Geographic Magazine, which was published in August 1930 as The Conquest of Antarctica By Air. It's listed in Beyond the Mountains of Madness on page 14 under 'More Reading'.
Issues are available on eBay all the time, starting at around a mere $6 (my copy is from there). But you can also download it as a 172-page PDF, which although lacking in resolution, will give you a way to read Byrd's extensive details on the expedition without adding yet another book to your library.
Yesterday I sent out six telegrams to my prospective players, each containing a short invitation to join the upcoming 1933 Starkweather-Moore Expedition to the Antarctic, it ends by stating that I'll be sending along more information. Tomorrow I'm sending en envelope containing two articles about the expedition, a period-correct map, a passport and two letters, one from Professor Moore (3 pages, in the hand writing of H.P. Lovecraft himself), and a short bravura note from Starkweather.
The penguin is a USB key containing a custom 40-page National Geographic from 1931, covering the Miskatonic expedition, interspersed with photos from the mountains and Lake's camp (this is an edited version of the Antarctic guide from the BtMoM book, from which I removed all rules and anything that can spoil the story).
There's also a 12-minute recording of the Wireless transmissions from Lake's camp (I cut up a 'radio play' and aged the recording significantly, and overlaid it with appropriate sound effects, such as actual barking sled dogs), as well as a 20-minute recording of Worldwide Wireless News's interviews (same with this, although I also interspersed it with musical interludes) with the expedition members and other coverage.
here's also a 10-minute Newsreel covering the expedition (Thank you HPLHS).
Furthermore I put together a 90-minute soundtrack consisting of tracks from a variety of composters, including Erdenstern, Goldenthal, Desplat, Goldsmith, Ligeti, Beltrami (and the sound of actual Antarctic wind).
Finally I included some radio plays of Lovecraft's stories and a version of the Trail of Cthulhu Player's Guide in which I removed all references to At the Mountains of Madness.
The package was received very well indeed, and caused one player's wife to exclaim that he had no other choice but to join the game.