Andre Breton's Manifesto of Surrealism

Surrealist Manifesto: Declaration of 1925

The three basic tenets of Ezra Pound's Imagist manifesto

An explanation of the Imagist manifesto

Amy Lowell expands on the tenets

Eugene Jolas's "Manifesto: The Revolution of the Word"

"To Make a Dadist Poem," Tristan Tzara

More from Dadaism

The Futurist Manifesto

Charles Olson's Projective Verse

Frank O'Hara's Personism: A Manifesto

The smart wiki entry on Art Manifestos

Wendell Berry's poem "Manifesto The Mad Farmer Liberation Front"

Jeff Gundy's "Manifesto of Anabaptist Surrealism, or Surrealist Anabaptism" from his essay "Heresy and the Individual Talent"

David Wright, "Poems Should Not Be"

Two quotes from Dylan Thomas' "Poetic Manifesto"

Charles Baudelaire's manifesto, "The Painter of Modern Life"

Jack Kerouac's "Essentials of Spontaneous Prose"

A Whole Course on Manifestos

A Book: "Manifesto: A Century of Isms"

A great review of said book

They promise all kinds of them at Manifestos.net

Some dudes named Marx and Engels and their manifesto

"Industrial Society and Its Future" (The Unabomber's Manifesto)