Minisumo
Branden writes –

Robothon is an annual event sponsored by the Seattle Robotics Society that is designed by and for hobby roboticists and Makers of all types. It is held every year at the Seattle Center, just north of Downtown. Robothon is completely free to everyone. Vendors will be on hand with Microcontrollers, BEAM robot kits, and other useful electronic parts. At this event, people from around the world come together to present new robotic technologies, share ideas, meet fellow robotic enthusiasts, show off their robotic creations, and compete in many robotic competitions and activities.

Robothon – September 21 – 23 – Seattle – Link.