There are some really innovative visualization mashups including Digg Charts, Digg City, Wheel of Upcomingand others. I actually find the ones built using Adobe Appollo (make sure you have it installed) to be less impressive than the pure Flash ones. This is kind of a surprise for me.
I already wrote about Digg Exposé, the mashup between Digg and Snap Shots. It looks like it has many fans but it needs more votes.
