Poetry
Poets.org
Is run by the American Academy of Poets and there are also thousands of poems archived here along with articles and poet biographies. A great place to start.
The Poetry Foundation
Poetry Foundation is the online component of Poetry Magazine. There are thousands of poems archived here along with poet bios and articles.Thanks for the link, Annik!
Columbia University Bartleby Library
Many poems and quotations from famous authors; “You might prefer to check this site out.” 
The Poetry Archives
Find poems written by all kinds of poets
