The British newspaper, the Guardian, has a regular (more or less) poetry workshop on their website. The latest exercise, on anti-praise poems, is up now. You will need to be quick if you want to submit your results for consideration. It has been up a day or two, and the deadline is May 7th (UK time). However, all the previous exercises and comments on the results are still on the site. It's a useful source of stimulating ideas, even if the deadlines are too short for you.
To link to the site, click here.