InkPad Notepad - Notes - To do This app is a convenient and easy way to deal with one of the biggest poetic pitfalls-- those times when you have a flash of inspiration but no pen and paper nearby. Instead of having to text notes to yourself (what I used to do), you can just type them into InkPad Notepad. Best part: the app autosaves, so you won't accidentally lose anything if you get distracted.

Merriam-Webster's Pocket Good old Merriam-Webster. Invaluable for when you can't remember the right word, or when you're not completely sure of all the connotations of the word you just wrote.

Advanced English & Thesaurus I've found this to be one of the most effective thesaurus apps around. Poetry is all about word choice, so a good thesaurus helps a lot in finding the most appropriate synonym you can. (Just don't overuse it!)

B-Rhymes Dictionary For anyone who writes more traditional rhyming forms. The reason I prefer this to any of the other available rhyming dictionaries is that it gives you slant rhymes and near-rhymes as well, which is sometimes what a poem needs, stylistically.

Classic Text To Speech Engine A lot of poems demand to be read aloud, so you have to pay attention to the rhythm as you're writing. But what if you're too self-conscious or too busy to recite for yourself? Make your phone do it instead. And you don't have to listen to that creepy computer voice (you know the one) if you don't want to-- Classic Text to Speech Engine offers more than forty different voices and twenty-five languages.

Poet’s Pad™ - Creative Writing Not every function of Poet's Pad is as good as some other individual apps are--e.g., the thesaurus--but if you want a bunch of poetry tools all in one place, it can be a major time-saver. Also comes with an idea generator.