PlaceIMG is a web app that allows you to easily find free images to use in your next project. Simply select your required dimensions, category, and add an optional filter, then you’re done.
It doesn’t allow you to do a text search, although you can cycle through pictures matching your criteria with a refresh button. They even have plugins for your favorite CMS (WordPress and PyroCMS for example.)
You may be wondering how it’s free? It only returns photos with Creative Common licenses so you’ll still have to attribute the original photographer and you may not be able to use the image in a commercial project. Even so, it’s a pretty cool tool (now why didn’t I think of that?!)