Tracery is a super-simple tool and language to generate text by Kate Compton. It's been used by middle school students, humanities professors, indie game developers, professional bot makers, and lots of regular people, too.
Douglas Luman's Applied Poetics, a computational writing platform which features 50 different tools you can use to transform texts.
The N+7 procedure, invented by Jean Lescure of Oulipo, involves replacing each noun in a text with the seventh one following it in a dictionary. (In French, it is also referred to as the 'S+7' procedure.) Here you can enter an English text and 15 alternative texts will be generated, from N+1, which replaces each noun with the next one in the dictionary, to N+15, which takes the 15th noun following.
Sonnetizer is a program written by Ross Goodwin that generates 14-line rhyming sonnets from any text corpus.
This site will help you make a Twitterbot! They're easy to make and free to run. To use it, create a Twitter account for your bot to run under and then sign in. The bots are written in Tracery.