CADing && Coding - A learning resource for AutoCAD Programming and Customization.Contains AutoCAD.Net programming with C#, VBA Programming, DIESEL Macros and AutoCAD Tips & Tricks. - http://cadingandcoding.blogspot.com
ObjectARX & Dummies - Talk about programming using .NET framework and ObjectARX Autodesk API. - http://arxdummies.blogspot.com/
Through the Interface - Site made by Autodesk member that contain information to ObjectARX API development and code samples. - http://through-the-interface.typepad.com/
Open Design Alliance - An association of CAD customers and vendors committed to promoting Autodesk's AutoCAD DWG drawing file format as an open, industry-standard format for the exchange of CAD drawings. - http://www.opendesign.com/
Py_acad - A free software module that makes it possible to extend AutoCAD with the Python programming language, in a similar way as with AutoLISP. - http://pyacad.sourceforge.net/
ARX LT SDK - An extension to AutoCAD LT to enables the ObjectARX API as with the standard version of AutoCAD. - http://www.cadaware.com/
AutoCAD Exposed - Information about undocumented features of AutoCAD, such as commands, system variables, and functions of the ADS, ARX, and AutoLISP programming interfaces. - http://www.manusoft.com/Resources/AcadExposed/index.stm
AutoCAD Developers Group Europe - A non-profit association of software developers who are working on applications around AutoCAD. - http://www.adge.ch/