Attention all map lovers: Stamen Design's new Mapstack service is hard to describe but worth delving into and playing around with. Is it an app? Not really; there's nothing to download. You just go to the website and jump right in. Is it a graphics program? Sort of; the controls work a bit like Photoshop, with sliders popping up in boxes when you want to edit a layer.

It's all there for free, accessible even from a tablet: worldwide map data with tons of graphic tools and the ability to link five layers. Concoct practically any kind of map you can imagine. Like it? Click on it to save it as an image. Click again to email it or Facebook it or load it onto your tumblr site. It's pretty cool.

According to the website, the service is "part of the CityTracking project, funded by the Knight Foundation, in which Stamen is building web services and open source tools to display public data in easy-to-understand, highly visual ways." According to users who have tried it, it's a ton of fun.