Check out Workshops on the Forward Poetry site for poetry structures explained ... to the 'n'th degree ...
Echo Verse, Triolet, Rondeau, Pantoum, you see, I do actually recognise many forms ... but Forward Poetry seem to know them all ... the choices are endless. I did fancy the 'Diamante' Poem, which, to be honest, I'd hadn't ever heard of:
'The diamante, or diamond poem, is a style of poetry made up of 6 lines, using only 13 words and forms the shape of a diamond. The poem starts with one subject and evolves into a different subject, the exact opposite of the starting subject. The diamante poem is classed as a modern poetry style, which was developed by American writer, Iris Tiedt, in the 1960s.' [Forward Poetry]
The fixed forms are explained well - and I'd definitely advise you have a go ... tempt your thoughts into one of the structures. Doing this forces you to be very strict with your content. When adding strong rhyme to repeated lines emphasises content. Fixed form is great for practicing writing poetry - a bit like skiing down the mountain behind an experienced skier - the path is already chosen for you so you can concentrate on content, mood, tone, sounds, voice, style. Fitting your words into a strict structure also aids recognition of rhythms which comes into play when writing free verse.