The Academy of American Poets
Supports American poetry "through a wide variety of literary programs and prizes." The site also includes several interesting articles and a good FAQ for poets.

Canadian Poetry Association
"The main aims... are: To promote the reading, writing, publishing and preservation of poetry in Canada through the individual efforts of members; to promote communication among poets, publishers and the general public; to encourage leadership and participation from members and to encourage the formation and development of autonomous local chapters."

The League of Canadian Poets
"Canada's national organization serving professionally published and practising poets."

The Poetry Society
"Helping poets and poetry thrive, The Poetry Society is one of Britain's fastest growing arts organisations."