Oh wow, I just went to http://www.popfly.com to try the mashup stuff, and it was a BLAST. I tried out the photo mash-ups and it was awesome, I am going to show it to some of my friends online.
I haven't tired to use that Visual Studio 2008 Express thingie with the popfly add-in, but I added it to my computer. I think that I will try it later today after I get back from hitting the waves, it looks like a lot of fun.