Free Poetry Resources
Maybe poetry should fall under literature, but I love poetry, and I spend so much time on it with my students and my children that it basically becomes its own separate subject. Poetry is the distillation of thoughts into concise, beautiful writing, and I am hear for it.
Free Poetry Resources for Elementary Students
The Poetry Foundation is an almost hundred year old nonprofit dedicated to publishing poetry, mostly through Poetry Magazine. They have a whole section of their website designed for children.
Poets.com is another website that compiles poems, and they also have a section of poems for children.
Poetry4Kids is a website curated by children's poet Kenn Nesbitt. Many of the poems on this site are by him, but he also provides plenty of other poems written by his friends and in the public domain. Many of these poems are silly, and perfect for younger children.
Free Poetry Resources for Middle and High School Students
The Poetry Foundation maintains a website with thousands upon thousands of poems, many of the published over the past hundred years in Poetry Magazine. Others they have the rights to in other ways, or are in the public domain. Some of the poems are read aloud by the authors, even. They also curate lists of poems, have biographies of poets, and provide analytical discussions of poetry and specific poems. Grown-ups should be aware that many poems deal with mature and sensitive topics.