Kikiyama’s surreal-horror dōjin game Yume Nikki has an official manga adaptation, illustrated by Hitoshi Tomizawa (famous for the biopunk manga, Alien 9, and Milk Closet). You can read the first chapter of Yume NIkki here.

EDIT June 22, 2013: Previous link no longer works. You can now find the manga here. Thanks to Satoshi Mochida for the information!