http://www.digitaltutors.com/software/AutoCAD-tutorials

www.proetutorials.com/

https://catiatutor.com/

http://www.catia.com.pl/tutorial/part_design.pdf

http://catiav5v6videotutorials.caddsoftsolutions.com/2011/10/catia-v5-basics-getting-started.html

http://www.cgonlinetutorials.com/tutorials/catia-tutorials.html

www.solidworkstutorials.com/

https://www.youtube.com/user/solidworks

www.solidworkslessons.info/

www.creotutorial.com/

Creo tutorials-You Tube (https://www.youtube.com/playlist?list=PLgh-maHw9pPc557b-dHMZ43dkTMAY5AKR)

Apart from these links, go to the HELP section of your software and practice examples,option wise.  Use HELP Files in any CAD Softwares like SolidWorks/Catia/PTC Creo/Pro E, etc.

Go to the official websites of any of these softwares and post in your doubts at the help sections available.  

The entire details for Pragyan Design Challenge can be downloaded here