blender.org - The official website of the Blender Foundation.
blendernation.com - Fresh Blender News, Every Day.
durian.blender.org - Project Durian, the Blender Foundation's third Open-Movie project.
mango.blender.org - Project Mango, the Blender Foundation's fourth Open-Movie project, focusing on visual effects and compositing tools.
blenderartists.org/forum - The BlenderArtists.org forums, where Blenderheads can talk, participate in group projects, and get feedback from other Blenderheads.
graphicall.org - Tonnes of different Blender builds in development, every day. Build-types range from Official releases, In-Development "Trunk" builds, Google Summer of Code, Experimental, and Optimized builds. The site now includes builds for GIMP, Inkscape and other open-source software.
cgcookie.com/blender - Run by professional Blenderheads such as Wes Burke and Jonathan Williamson, this site has tutorials covering almost every aspect of Blender.
blenderguru.com - Similar to CGCookie, but Andrew Price specializes in special effects, rendering and simulations.
netcarshow.com - A recent addition to my repertoire. A great place to find tonnes of reference images for almost all car makes and quite a few models.
blendswap.com - The largest, most well-known repository for Blender models. Requires an account in order to download blend files; most files are also under Creative Commons licensing.
Fellow Blenderheads (more to follow)
deniszholob.99k.org - Also known as DDD on BlenderArtists.