Part of me feels guilty cutting up magazines to make collages out of... but the other part of me doesn't care, so I do it anyways.
Unless of course, the magazine is really, really nice. For instance, I wouldn't cut up Human Being Journal. Their designs are too lovely. HB Journal is produced by Need Supply Co. and perfects the right amount of editorial, art, and design. I picked one up at MOCA last weekend; you can snag one from their site here.
Anyways, these three gems hang proudly above my desk. Collages are one of the best DIYs as they're inexpensive and you can let your creativity run wild. They're sort of like clusterfucks of moodboard images all smashed together, but in a nice way.