Many people have mentioned Nine-Inch Nails' "Ghosts I-IV" project, two hours of impulsive instrumental soundscapes by Trent Reznor, Atticus Ross, and Alan Moulder, with some help from Alessandro Cortini, Adrian Belew, and Brian Viglione. Aside from being an interesting experiment in music distribution, it features a 40-page downloadable .PDF booklet of photographs by Phillip Graybill and Rob Sheridan that NIN calls "visual aesthetic accompaniments to the music from the recording process and the outside world."
You can stream the music from the site or download or purchase multiple versions (although the $300 Ultra-Deluxe Limited-Edition package is sold out already) in a variety of formats. There is no charge to download the .PDF alone.
Mike (Thanks to David Rea, Michael Arcila and others)