Some sources for contemporary Japanese poetry:

The following are a few sites in Japanese, though much of the poetic activity in Japan still takes place off-line. (Neither Shichosha nor its journal, Gendaishitecho - major sources of Japanese poetry - have websites.)

Publishers:
Shoshi Yamada　- contemporary, experimental poetry - mostly Japanese, as well as many works in translation.
Midnight Press - journal and books
Seidosha - also publishes the journal Eureka
Azami Shobou - small press run by Fujitomi Yasuo.

Journals:
in/out 
rain tree
sagana
δ (delta)   
shigaku

Poets:
Hirata Toshiko - (Wikipedia)
Nomura Kiwao
Hiraide Takashi - (Wikipedia)
Yoshimasu Gozo - a selection of poems
Yagawa Sumiko - (Hatena Diary)
Koike Masayo - (rain tree)
Yoshioka Minoru

...and a few Modernists:
Sagawa Chika
Kitasono Katsue