AutoCAD

Cadopolis.com - Commercial portal for products and services related to AutoCAD, with add-ons, software downloads, forums and links.
http://www.cadopolis.com/

CAD Forum - Database of tips and tricks for AutoCAD, AutoCAD LT, 3D Studio, Inventor and other products by Autodesk and HP.
http://www.cadforum.cz/

Cadville - Free portal for AutoCAD and Autodesk product users, with news, product reviews, an events calendar, and links to other resources.
http://www.cadville.com/

Cadalyst: Bugwatch - A monthly column documenting old and new bugs in AutoCAD and their workarounds or fixes, where available.
http://www.cadalyst.com/cadalyst/article/articleList.jsp?categoryId=3032

Autodesk Point A - A second portal by Autodesk that helps designers to locate industry resources, with additional services for subscribers.
http://pointA.autodesk.com/

EllenFinkelstein.com - AutoCAD tips and tutorials, the features of the latest AutoCAD release, a free monthly AutoCAD Tips Newsletter, and the AutoCAD Tips Blog.
http://www.ellenfinkelstein.com/

AutoCADder blog - News and comments about AutoCAD, LT, Inventor and other Autodesk software, product releases, and technology.
http://autocadder.blogspot.com/

Autodesk Blogs - A series of Blogs from Autodesk employees about various topics related to the company and its products.
http://autodesk.blogs.com/

Autocad Central - A series of basic AutoCAD tutorials, and a discussion forum for questions and answers.
http://www.autocadcentral.com/

Autocadzone - Free AutoCAD help and tips, tutorials and video tutorials, and student examples of 3D models.
http://www.eezylearn.pwp.blueyonder.co.uk/

The CAD Depot - A repository of freeware and shareware tools for use with AutoCAD and other CAD systems.
http://www.caddepot.com/

The CAD Geek Blog - Discussing popular Autodesk products such as AutoCAD, Civil 3D, Map 3D, and Land Desktop, by AUGI World columnist Donnie Gladfelter.
http://thecadgeek.com/blog/

The Autodesk File - A history of Autodesk and AutoCAD by John Walker, the founder of Autodesk.
http://www.fourmilab.ch/autofile/

CAD Panel - A source for AutoCAD users to download free AutoLISP routines, hatch patterns, material libraries, tips and techniques, extra help, and articles.
http://www.cadpanel.com/