There is no shortage of reading material for haiku and horror fans, either online or in print. For starters, the new issue of Champagne Shivers just came out (the last issue that will be edited by Cathy Buburuz, unfortunately), with a great cover by Mark Crittenden and stories and poems by Lucien Spelman, Brian Rosenberger, and Therese Arkenberg, among many others.
The March issue of The Heron's Nest is online. Page 3 has a horror-ish haiku by George Swede.
Niteblade has also just put out a March issue, containing lots of dark poetry and fiction. As always, you can read the issue for free online, or buy an ad-free PDF copy for just a few bucks.
J. Bruce Fuller's haiku sequence chapbook, 28 Blackbirds at the End of the World, is on sale now from Bandersnatch Books for $9.50. The sequence originally appeared in Scifaikuest and was subsequently nominated for a Rhysling Award.