when you jump shake your remote. It will cause your character to spin and float for just a bit. Sometimes you can spin twice in a single jump which really extends it.

Get a boss, they're just shells but they are pretty cool especially for NSMBWii

It's partcularly useful when you are tiny Mario.  If you watch some of the Super Skills videos you can see it used to great effect. I mostly just used it for getting 1-ups at the end of the stage and for the occasional mis-timed jump.

Once you've beaten the game, I highly recommend you go back and watch all the 'super skills' videos, and some of the 'infinite lives'. Infact, watch them all. The first time I saw the tester using the longer jump thing I thought he was cheating

THe answer is no.

Also that boxart is freaking awesome.