Several years ago, a wonderful kindergartner teacher whose face I can recall but whose name escapes me told me of this method she uses to help children conceptualize odd and even numbers. She said the odd numbers are like old school buses, the ones with a hood out front, and even numbers are like the newer ones that are straight down with no hood. She then demonstrated it using small colored blocks.
There's a lot more to odd and even numbers than meets the eye. Dr. Maths has an interesting history of them and for the real math nuts here's a way more complicated explanation at Wolfram Maths World. And here's a wonderful article in Wired, a British journal about how we are hard wired to prefer even numbers; ain't that the truth!
Meanwhile I continue my mission to turn math into the much more grammatically correct and sensible maths.