In my old job as a Web strategist in DC, I had the pleasure to work with the really smart and friendly (and prolific) folks at the Pew Internet Project.
They publish, with amazing regularity, top-notch research on how people use the Web. Their latest article, which I’m happy to see is getting a lot of attention among bloggers, is called “Spam: How it is hurting email and degrading life on the Internet.”