Please recommend interesting 4-5 star Linked Data Sets

Hi all,
I'm putting together a talk for the upcoming SemTech conference in San Francisco on behalf of the GLD WG and the status of publishing open government data sets worldwide.  I hope this is a no brainer.  

Can you please respond with a data set name(s), a 1-2 sentence description & ideally a URL of any 4 or 5 star Linked Data sets that you know about, can brag about because you're doing it, or think would be of interest to others.  

We hope to be announcing the availability of the environmental datasets our team worked on during the last 12 mos.  FYI, we're in the security planning process with EPA and hope to have some good news to share in the coming months.  

Step by step we are all getting there. Hopefully the working group & those lurking on this list are demonstrating the value of these data sets within verticals & sub-domains with which we work.  

I ask for your assistance with some profile raising so that more managers will feel comfortable that there is a thriving ecosystem of data publishers & consumers.  That will produce the virtuous circle needed to expand the Web of Data.  TIA.  

Have a nice weekend!

Cheers,

Bernadette Hyland, co-chair 
W3C Government Linked Data Working Group
Charter: http://www.w3.org/2011/gld/