That headline implies that I know how to make my own New Super Mario Bros. Wii levels. I totally don't. However, if didn't have to finish figuring out how to make my own Wario Ware DIY levels first so that I can review the game, I'd dedicate some time to figuring out how to use Reggie!.
Reggie! is a PC/Mac/Linux program that lets you edit and create New Super Mario Bros. Wii levels, which can then be played on the Wii using an original (meaning, not pirated) copy of the game and the Wii Homebrew app Riivolution. Reggie has been around for a while, but the latest version was just posted a few days ago, and it looks pretty awesome. The promise of actual sprite editing is what I'm most excited about.
Once again, Nintendo fans have outdone Nintendo themselves. Hackers are constantly adding new characters to Smash Bros. Brawl, teams of programmers work to create translation patches for games like Mother 3 and Fatal Frame 4, and now they've made us a level editor that rivals those used by professional game developers -- all for no other reason than the love of the game(s). Needless to say, Reggie Fils-Aime could learn a thing or two about what Nintendo fans want from these impressive, dedicated individuals. He'd also do well to pay them for their work, and release this stuff to the commercial market. There is no telling how much money Nintendo could make off all this stuff.
And yeah, you can go ahead and add "homebrew awesomeness" to your list of reasons to dust off your Wii this year.