For part of my intro to Mechanical Prototyping class in fall 2011, I was on a team that designed and fabricated a 3D printed 6-legged walker using the Theo Jansen leg inkage. We designed it to be printed fully assembled by making use of support material that is dissolved away after printing. This let us print moveable linkages. Once it came out of the lye bath, we just added motors and batteries and it started walking.
For a more thorough description of our process and results, please take a look at our design report: RP_Crawler_Report (Download PDF)