Every issue of the Journal of Humanistic Mathematics contains poetry.
The Spring 2016 issue of TalkingWriting has more than a score of mathy poems.
This blog has offered math-linked poetry online since 2010, now with over 800 posts. Scroll down to browse OR use the SEARCH box to look for poems with a particular mathematical image. The lower right-hand-column offers key-words that can be useful search terms.