New Super Mario Bros. Wii (Wii)
After beating World 8, a new "save" option will replace "quick save" on the map screen menu.
Spin on the ground (shake the Wii Remote) near a dancing flower and one coin will pop out. You can do this once per flower.
Five bonus coins
If a multi-coin block is still active after you collect 10 coins from it, the final hit will release five coins.
Finish a level with 99 lives, and Mario will have his hat off when he is back on the map screen. As long as you stay at 99 lives, Mario will go through the levels without a hat. Propeller and Penguin Mario will still have their head covers, however.
Unlock World 9
Beat World 8 to unlock World 9. In World 9, each level is blocked off until you collect all the Star Coins in the corresponding World. For example, collect all the Star Coins in World 4 to open up 9-4.