The Super Mario Bros. 3 e-cards were pretty awesome, IMO.
Although there were only two small sets released in the US, there were a LOT more cards released in Japan, including several new STAGES!

My friend and I got a nearly full set a few years ago when I was still living in Japan by buying some sealed boxes of (random) e-card packs on Yahoo Auctions.

More info on the Mario cards here:

http://www.mariowiki.com/Super_Mario_Advance_4_e-Cards

I also have some Japanese F-Zero e-cards and Mega Man Zero 3 e-cards, but I'm not sure how they are used in conjunction with their respective games.