Data sources: Website and web server stats from Netcraft. Domain name stats from Verisign and Webhosting.info. Internet user stats from Internet World Stats. Web browser stats from Net Applications. Email stats from Radicati Group. Spam stats from McAfee. Malware stats from Symantec (and here) and McAfee. Online video stats from Comscore, Sysomos and YouTube. Photo stats from Flickr and Facebook. Social media stats from BlogPulse, Pingdom (here and here), Twittercounter, Facebook and GigaOm.
Great review of the amazing volume, momentum and trends of Internet usage. Some stats that caught my eye include email, photo and social media usage.