MakerBot has just announced the release of a new free design tool called the Cookie Cutter Customizer. It's available on Thingiverse and it creates a 3D printable STL file based on your own hand-drawn art.
In order to create your cookie cutter you will need to sign up for a free Thingiverse account. Once you have created your account you can select "Open Thingiverse Customizer" from this page to create a cookie cutter. It's browser-based, so you can work right from your computer.
Once inside the customizer, users can draw a cookie cutter of their own by moving their mouse, or customize a bunny template provided by Thingiverse. The process isn't perfect; it's very difficult to get intricate shapes, or even draw a perfect circle. If you're patient enough to tinker with it though, you can get decent results. The Thingiverse customizer also allows you to set the wall thickness and height of your cookie cutter.
At this time it is not possible to order the physical cookie cutter from Thingiverse, you can only download the STL file. If you do not have a 3D printer at home and want to buy the cookie cutter you create, you can upload the Thingiverse STL file to Shapeways and place an order with them.
Makerbot isn't the only company to release this type of user-friendly design app. Cubify just announced their Summer Sunglass Design Challenge and Party Glasses App. The winner of that challenge gets their very own Cube 3D printer.