These two are my primary source of 3D printing-related information:
3D Printing Industry (my personal favorite) - 3DPI works with a dedicated team of writers with experience and a keen interest in this technology field technology. Their remit is to provide reliable news, interviews and insight about the latest trends in 3D printing across the board, including the pioneering home users, the maker community and industrialists. http://3dprintingindustry.com/
3D Printer World - 3D Printer World is an online resource providing news coverage, original feature stories and analysis for 3D printer users and 3D object designers. Serving both commercial and personal users, our mission is to explore and promote the use of additive manufacturing as a catalyst for creativity and economic growth. http://www.3dprinterworld.com/
Personalize -The 3D Printing Hub - We'll ... keep you up to date with relevant information and news stories from the industrial side of 3D printing, particularly when it has a real impact on the makers and consumers looking to get involved.
Stratasys (used to be Objet before the companies merged) - Formed in 2012 by the merger of 3D printing companies Stratasys Inc. and Objet Ltd., the company’s systems include affordable desktop 3D printers for idea development, a range of systems for prototyping, and large production systems for direct digital manufacturing.
3D Systems - 3D Systems is a leading provider of 3D printing, rapid prototyping and direct manufacturing systems, as well as software and materials that transform CAD into actual physical parts. (Their consumer 3D printer is the Cube.)
Makerbot Industries - Founded in 2009, Brooklyn-based MakerBot® (www.makerbot.com) has grown to be a global leader in desktop 3D printing. ... There are over 13,000 MakerBot Desktop 3D Printers in use by engineers, designers, researchers, and people who just like to make things. (Their consumer machine, not surprisingly, it the Makerbot.)
PrintrBot: RepRap & MakerBot Builders - An affordable 3D printer that you can assemble in a couple of hours. ... We [also] have a Meetup Group ... in Northern California. Mission = A 3D printer in every home (and school). (Consumer machine is the Printrbot and its relatives. Also has a local(ish) meetup in Lincoln, CA.)
3D Printing on Campus -3D Printing on Campus is a project of Stratasys Ltd., innovator of 3D printing systems and solutions. This page is primarily a space for educators and students to learn about, share and discuss additive manufacturing, CAD and 3D printing in relation to educational applications. Research projects, lab work, grant programs, STEM applications, design and engineering curriculum and the latest educational news are some of the topics you can explore on this page.
3d Printing and Physibles - Physible's are 3d designs or plans for 3d objects, download a physible off the Internet and print it as a physical object at home, this could be anything from clothes, jewelery, furniture to car engines.. Sounds like science fiction? it already exists!
Dreambox (update 2.13.14: Now Twindom) - Right here in Berkeley, it's the first 3D printing vending machine! Dreambox is a 3D printing service that will help you materialize whatever it is that you want to make. If you're looking to visualize an idea of yours, we can help you take a pencil-and-paper concept all the way to 3D printed object.
You will find many of these links already in the sidebar of this blog. Stay tuned - it is likely I will be updating this list! :)