Maker Faire was a strange place, it reminded me of Burning Man (without drugs), or maybe a sci-fi convention (without Star Trek uniforms). The crowd was a mix of all kinds of people. I saw lots of punk rock and tattooed kids. I also saw religious Muslims and Jews, together in one space, in Dearborn. It was like, peace, love, and robots, man.
Here are a few things that I thought were neat.
Miniature V-4 engine, made by a guy from the Metro Detroit Metal Machining Club.It runs!
Electric scooters by Current Motors. They claim a range of about 45 miles from a 4.6kWh battery pack, with a top speed of 55mph. Cost: $6500.
This cute hearse and "mad scientist" are promoting a product which is claimed to preserve jack-o-lanterns so they won't rot so quickly on your porch. I had no idea I needed such a product. Dr. Frybrain's Pumpkin Embalmer.
A really neat 4-rotor remote controlled helicopter (quadrocopter). It uses an on-board micro-controller (Arduino) to trim the motors to maintain attitude, using inputs from a 6-axis inertial sensor board.
Over at the TARDEC display, the Army shows off a concept for a light armored ground vehicle.
This Gladiator robotic vehicle was doing peace-time duty writing people's names on a dry erase board. In battle, it can be used to remotely manipulate road-side bombs and suspicious packages. They can also be mounted with weapons.
This hilarious car, the "Sashimi Tabernacle Choir", is a 1984 Volvo 240 sedan which has been decorated by a bunch of those cheesy dancing lobsters and singing bass that you can order on late night TV infomercials. The effect is hypnotic--when the sound system plays, all of the lobsters and fish sing and dance in sync. If you go to the linked web site, you see that this was a huge engineering project--they actually wired each fish and lobster into a central relay system, and wrote software to control all the motion.
The centerpiece, the main attraction I would say, of Maker Faire Detroit was the Life Size Mousetrap installation. A strange, wacky, and slightly disturbing mix of childhood memories, tattooed punk rock burlesque girls, welded steel, clowns, and a very crushed Chevy Astro minivan. This thing travels around the country like a mini-circus, smashing things.
Esmerelda Strange, the one-woman punk/polka band who warmed up the crowd for the Life Size Mousetrap piece. She seemed bored with the whole thing. She sang in a monotone and had way too many tattoos.The Life Size Mousetrap in action.
Rose "The Mouse", the ringleader's wife and head merchandiser. 
Another highlight was Big Dog, a gigantic pedal powered quadracycle with propane flame belcher. I'm not sure why fire was involved, but the design and construction of this beast is amazing.
A Big Dog drive-by, slightly out of focus (sorry).
Two examples of Amick wind assisted electric vehicles, without their large vertical airfoils. The concept is to use energy from cross-wind to help propel the car, similar to how a sailboat can pull energy from the wind with its airfoil, the sail. 
Yet another NEV (Neighborhood Electric Vehicle, limited to 25mph) offered by EcoV. This is a prototype vehicle, commercial production is supposed to start later this year.
Moving inside, near the Oscar Meyer Wienermobile I found a guy showing of amazing miniature mechanisms, including air-powered steam engine models. He had a hightly detailed, running miniature model of a steam-age machine shop, much like the full size one you can tour in Greenfield Village.