A list of journals that publish micropoetry. This post is cumulative and journals can be added at any time. Please feel free to make micro_poetics aware of any journals not listed in the comments below.
Tinywords.com - daily magazine of haiku and micropoetry
Acorn - biannual journal dedicated to contemporary English language haiku
Failed Haiku - A journal of english senryu (hat tip to @billysince71)