Feel free to edit this and add any ones you come across!

Business

See the WordPress.org Showcase at http://wordpress.org/showcase.

Universities

See the WordPress.org Showcase College tag, found at: http://wordpress.org/showcase/tag/college/

Media

See this section of the Showcase: http://wordpress.org/showcase/tag/news/

Popular

See these two Showcase tags:

http://wordpress.org/showcase/tag/celebrities/ http://wordpress.org/showcase/tag/entertainment/

Magazines

• Arena - http://www.arenamagazine.co.uk/
• Adotas - http://www.adotas.com/
• Complex - http://www.complex.com/blogs/
• People - http://offtherack.people.com/
• XXL Magazine - http://xxlmag.com/

Geek

• The Apple Blog - http://theappleblog.com/
• Canonical Blog - http://blog.canonical.com/
• GNOME - http://blogs.gnome.org/ (WP Mu)
• Google Sightseeing - http://googlesightseeing.com/
• HotForWords - http://www.hotforwords.com/
• LaughingSquid - http://laughingsquid.com/
• Mandriva - http://blog.mandriva.com/
• Mark Shuttleworth (Ubuntu fame) - http://www.markshuttleworth.com/
• Meraki - http://meraki.com/blog/
• Mitch Kapor - http://blog.kapor.com/
• Mozilla - http://blog.mozilla.com/ (WP Mu), http://developer.mozilla.org/devnews/ and many others
• Netstumbler - http://netstumbler.com/
• OpenID - http://openid.net/
• SitePoint - http://sitepoint.com/ (all blogs)
• Surfin' Safari - http://webkit.org/blog/
• TechCrunch - http://www.techcrunch.com/ (and all other *crunch sites)
• TechRepublic - http://techrepublic.com/ (CNET)
• Balkhis Inc. - http://balkhis.com/
• Tunesies - http://tunesies.online
• ARWebZone - http://arwebzone.com

Culture

See this section in the Showcase: http://wordpress.org/showcase/tag/culture/

Government and Politics

See this section in the Showcase: http://wordpress.org/showcase/tag/politics/

Remarkable Design

• 2advanced - http://www.plat4m.com/
• Colour Lovers - http://www.colourlovers.com/blog/

Blogging Networks

• 9Rules - http://9rules.com
• b5 Media - http://b5media.com
• Digital Photography Blogs - http://dpblogs.com
• Niner Niner - http://ninerniner.com
• Wurk - http://wurk.net

WP MU Usage

• All Things D - http://allthingsd.com
• Animation Blogspot - http://animationblogspot.com
• Edublogs - http://edublogs.org
• Freie Universitaet Berlin - http://blogs.fu-berlin.de
• Harvard - http://blogs.law.harvard.edu/home
• LeMonde newspaper - http://www.lemonde.fr/blogs
• Overstock.com - http://community.overstock.com/blogs/
• TUIfly.com Airline - http://www.tuifly.com/blog
• University of Calgary - http://ucalgaryblogs.ca/

Products and Famous Startups

• Magnetk / SFTP Drive - http://blog.magnetk.com
• Mahalo - http://blog.mahalo.com
• Meebo - http://blog.meebo.com
• Mint - http://blog.mint.com/blog/
• PBWiki - http://blog.pbwiki.com
• Renkoo - http://renkoo.wordpress.com
• SlideShare - http://blog.slideshare.net
• Smugmug - http://blogs.smugmug.com
• Sony Playstation - http://blog.us.playstation.com
• Sphere - http://sphere.wordpress.com
• The Robot Co-op - http://blog.robotcoop.com
• Viddler - http://blog.viddler.com
• Wesabe - http://blog.wesabe.com

Large Hosting Companies

• Dreamhost
• Layered Tech
• Lunar Pages
• Media Temple
• PEER 1
• Rackspace
• ServerBeach
• The Planet / EV1Servers
• UKHost4u

To Watch

• ChickSpeak
• Constitution Live!
• MobLogic
• Wallstrip
• Sydney Happy Hour