Undocumented Commands Tutorials
Convert AutoCAD Units Using -DWGUNITS - undocumented command method, questions sequence to set new setups in AutoCAD, Edwin Prakoso, CAD Notes, Mar 19, 2013

Generate a Preview by acdbMakeDrawingPreview - undocumented acblock.crx function in AutoCAD 2013 makes drawing preview image in given database using model space table record block, Xiaodong Liang, AutoCAD DevBlog, Feb 27, 2013

10 AutoCAD Commands You Have Either Forgotten or Never Knew (Update) - XOPEN, TRACE, SOLID, SETBYLAYER, REVERSE, TSPACEINVADERS, RK McSwain, CAD Panacea, May 14, 2012

10 AutoCAD Commands You Have Either Forgotten or Never Knew - CONVERTPOLY, DBLIST, XOPEN, TRACE, SOLID, SETBYLAYER, RK McSwain, CAD Panacea, Aug 3, 2009

Info on Sortents in AutoCAD 2005 and On - selection, Osnap, regen, and plot are still in use while redraw, slide and PSOUT are obsolete, JTB World, May 4, 2007

Acad 07: Undocumented MaterialAssign Command - the command attaches material stored in CMaterial system variable to the objects, Ralph Grabowski, WorldCAD Access, October 30, 2006

AutoCAD R2004 Easter Egg - discover the developers' hidden message inside the latest version, HyperPics, July 2003

AutoCAD Exposed - undocumented AutoCAD commands, system variables, AutoLISP, Owen Wengerd, Manusoft