Using what Jack Kerouac called the "American Haiku type... Simple 3-line poems... free of all poetic trickery" (see his Book of Haikus edited by Regina Weinreich), draw out three short lines from any text to shape a tiny poem. The only "rule" is that all three lines need to come directly from the text (or texts) you set aside to use for this exercise. Don't worry about syllables or writing a poem that feels finished. Just look for interesting images, ear-catching phrases, and so on.
Try drawing lines from a newspaper article or magazine ad or travel folder or cereal box or textbook or piece of junk mail... When I give this exercise to students, I also give them a page or two from a magazine to use as a source text. It usually helps to limit yourself to a specific range of text--it's a good challenge to see what you can find within, say, the letters to the editor section of a newspaper on a given day.
I like to do this with any old piece of text that's close at hand when I have a moment of free time. I also do this with journal entries: I read through a page or two from one of my spiral notebooks and take just a few snippets to form a small poem. Generally, I use this exercise as a starting place to write a poem that ends up to be a little bit longer. I think the three-line limit is freeing because even when I feel really stuck, I can find three tiny lines to work with, and sometimes a poem grows from there.