I'm a regular user of your top 9, but the USGS site has never made it into my browser. I'll be sure to check it out!

I work for a small non-profit called HealthLandscape, and we manage a site (HealthLandscape.org) that compiles public-use data into a single mapping application. It's a pretty nifty tool to play around with, and many of the data that you mentioned are included and available for mapping. There's no cost, but you do have to register an email address. Users can create their own thematic maps like the ones you've included in your post.

We're about to debut HealthLandscape V3, and I'm very excited about it. It will be much more user-friendly and more interactive.

Thanks for letting me share, I'm a long-time SAS user and a big fan of the blogs.