WriteOnIt is a simple service that lets you caption and manipulate uploaded photos. Just like BigHugeLabs' Flickr toys project (story), it can take uploaded photos and stick them into magazine covers. It can also slyly insert them onto coffee mugs, billboards, art easels, and fake mirrors within ready-made photos.
You have very little control over the complicated bits, like transparency, placement, and cropping--which are all absent. However, with that simplicity you can very quickly put together something that both looks polished, and that could fool your viewer.
Of all the tools my favorite is the newspaper creator. You have five different periodicals to choose from including Time, Rolling Stone, and Wired. It'll take whatever photo you upload (up to 8MB) and stick it in the background. You can also change the headline and tagline underneath it, but that's the only other thing you can change.
Once you're done with any creation made on the site you can save it to your hard drive, or send it to a friend either by e-mail or through MySpace, Facebook, and Windows Live Spaces. There's also an option to publish it so that other WriteOnIt users can see it, which will put it into a bucket of recently uploaded photos and make it eligible for "battle" where users can vote on which result looks better.