LinkedIn Groups

3D Printing  14,218 members

3D Printing Guild
3,977 members

TCT + Personalize – 3D Printing & Additive Manufacturing Network
1,947 members

3D Printing at Home
1,204 members

3D Printing Entrepreneurs
940 members

Shapeways 3D Printing Community
822 members

2D and or 3D Top CAD Experts
25,860 members

” Additive Manufacturing (AM) ” – Rapid Prototyping ( RP ), Tooling and Manufacturing -3D Printing
4,814 members

Forums

RepRap – #reprap on freenode IRC; /r/Reprap on reddit

3DPrintBoard.com: Threads 1,273 Posts 5,435 Members 899

3DPrinting-Forums.com: Total posts 1555 • Total topics 585 • Total members 1005

SoliForum: Registered users: 4,621. Total number of topics: 4,919

Forum.3ders.org: Connected with the 3der.org 3D printing blog.

Shapeways Forum: 3D Printing Forum connected to the Shapeways ecommerce community.

Google+

3D Printing
Come and troubleshoot, show off, or post news!
63,385 members

Reddit:

r/3DPrinting News, information, links and fun things related to 3D printing, 3D printers, rapid manufacturing, desktop fabrication etc.

Websites:

YouMagine is an online community for everyone who’s eager to explore the world of 3D printing.

Ultimaker – “The Ultimaker is the new kid on the block for 3D printing which officially started selling in May 2011.” They also have a community forum.

MakerBot’s Thingiverse is a thriving design community for discovering, making, and sharing 3D printable things.

Feel free to leave a comment if we left any out!