Meta is my self-balancing ride-on robot. Here's the first video (5.5MB, DivX AVI) of it with myself and Cameron riding (27/Aug/2006).
Someone at linux.conf.au took a video of Linus Torvalds riding it.
For the curious, the source is available here. It builds with avr-gcc and runs on the Atmel ATMega16 8-bit microcontroller which is on the MOB board. The code is based on Trevor Blackwell's balancing algorithm and code (see his Building a Balancing Scooter page).
I did a presentation at LCA2007 on how to build your own. You can get the slides here or view the video of the presentation here.
I'm indebted to Paul Schulz for assisting me to build Meta. The design is trivial (bolt motors onto pieces of wood with metal brackets), but hardware isn't my thing!