(I have not evaluated the first 4, but they seem helpful)
(1) Glossary of Poetic Terms from Bob’s Byway
A Unique Guide for the Study of Poetry
(3) Representative Poetry Online, Glossary of Poetic Terms by Ian Lancashire, Department of English, University of Toronto
Version 3.0
(4) Cliffs Notes Literary Terms & Poetry Glossary
(5) A Glossary of Literary Terms by Jane Reichhold
(There is a strong Japanese influence in this glossary.)
(6) “Poetic form refers to various sets of “rules” followed by poems of certain types. The rules may describe such aspects as the rhythm or meter of the poem, its rhyme scheme, or its use of alliteration. This category contains articles discussing such concepts.”
A free online encyclopedia has almost 400 pages on what looks like traditional forms. I believe in the study of these forms, even if one only writes free verse. This goes far beyond discipline; the forms adapted to free verse can give unusual good music, rhetoric, and a host of other benefits. There are some very powerful ones with which every poet should develop familiarity (sonnet, pantoum, etc.).
John C. Mannone: The Art of Poetry 