I started my son on a Skuut balance bike at 2 years old, it's basically a small bicycle with no pedals. They are really popular in Europe and teach your kids to ride a regular bike without ever needing training wheels. They start by just sitting on the bike and pushing themselves along, eventually they start lifting up their feet and coasting a bit. Pretty quickly they are coasting down long hills etc. My son went right from his Skuut to a regular pedal bike with no problems. I really believe in the Balance Bike concept now.

Here's a short vid of my son on his Balance Bike:
My son is now 3.5 years old and I've been looking into a bike to get him started on. I was going to pick up a Yamaha PW50 then I came across the Oset electic bikes. After looking into them and talking to other Oset owners I decided to pick up a 12.5" Oset. Everyone said their kids learn faster on the Oset, they learn to stand quicker and develop better balancing skills. Because it's electric and whisper quiet you can get away with riding it in parks, your front yard, etc where you can't ride the gas setups, because of this they get a lot more time in the saddle.
I also liked that I can lay it in the back of my wife's car, no gas to spill, no hot muffler, no starting the engine etc. Runs a couple hrs on a charge and has a max speed of 15mph, you can adjust the governor from 0-15mph. I currently have his bike slowed down until better throttle/brake skills are learned. I really like the 36V 16" Oset so if my son takes to this one I'll most likely get the 36V as his next bike.

Here's a short vid of my boy on his new Oset taken at a local park, this was his 3rd time out on it. Here he tried standing on the pegs for the first time, we are still working on smooth throttle control/brake usage.
Hodakaguy