muccamukk is hosting an informal writing workshop using Ursula K. LeGuin's Steering the Craft here. I think those exercises are well-suited for poetry--they're really about exploring writing basics:

The topics covered are:

The sound of language

punctuation, syntax, the narrative sentence and paragraph

rhythm and repetition

adjectives and adverbs

tense and person of the verb

voice and point of view

implicit narration: imparting information

crowding, leaping, focus, and control

which I think are useful things to return to and practice equally for poets and prose writers.