Feel free to go check out any you might have missed the first time around. It's all right there on the Wii Shop, simply choose Wiiware, Genre, then Demo.
Wow, really? Impressive. I'd *almost* recommend you get one, but at this point in the Wii's lifespan, it may not be worth it. I got a 32GB one, and it's got tons of stuff on it. DLC for Guitar Hero and Rock Band, and like, 30+ Virtual Console and WiiWare games. And I've barely scratched the surface of the card.
I also got another 32GB card for my 3DS. I'm determined not to let myself run out of space on my Nintendo systems, lol.