There are a number of great books that will help you to develop a study of the sonnet.  A few of them include:

Jack Agueros.  Sonnets from the Puerto Rican.  (Hanging Loose Press, 1996)

Eavan Boland and Mark Strand.  The Making of a Poem.  (Norton, 2000).  There is a great study unit on both traditional and modern sonnets .

Paul Negri.  Great Sonnets.  (Dover Publications, 1994)

Ron Padgett.  The Teachers and Writers Handbook of Poetic Forms.  (Teachers and Writers Collaborative, 1987)

Alex Preminger and T.V. F. Brogan.  The New Princeton Encyclopedia of Poetry and Poetics.  (Princeton University Press, 1993)

William Shakespeare.  The Sonnets are available on-line at <http://shakespeare.about.com/arts/shakespeare/cs/sonnets/>

Helen Vendler.  The Art of Shakespeare's Sonnets. 
(Harvard University Press)