Engineering

https://www.eeweb.com/toolbox  tools for electrical and electronics

http://www.calculatoredge.com/ online tools (Calculators)

http://www.allaboutcircuits.com/tools/ for electronics

https://www.gnu.org/software/octave/about.html  alternative to Matlab

https://www.scilab.org/ alternative to Matlab

https://www.anylogic.com/downloads/ alternative to Matlab free for personal use

http://maxima.sourceforge.net/download.html  alternative to Matlab computer algebra system

http://gridzzly.com/  just for paper printout with some backgrounds will be helpful to draw circuit boards manually

http://www.engineeringtoolbox.com/

http://patrickjmt.com/  big collection of mathematics video lessons

https://www.eevblog.com/ big collection of how to video lessons

https://www.newscientist.com/subject/technology/ to know new things

https://www.popularmechanics.com/ to know new things

https://ocw.mit.edu/courses/find-by-topic/ video. audio, text materials

http://www.engineering.com/ for new inventions & software

http://adventure.howstuffworks.com/  for new inventions

http://www.eng-tips.com/ Forums

http://www.discovere.org/resources-downloads videos, slides, texts etc…

http://tryengineering.org/ to select your engineering college/ course

http://www.engineeringchallenges.org/  New technologies

https://www.technologyreview.com/ New technologies

https://nsdl.oercommons.org/   Science Digital Library

http://www.nptel.ac.in/ Lot of Multimedia resources

http://www.shender4.com/eng-links.htm  Calculators

https://www.wolframalpha.com/examples/science-and-technology/engineering/

http://www.thomasnet.com/suppliers/  to search engineering parts/goods suppliers

http://www.globalspec.com/productfinder?frmtrk=global-nav to search engineering parts/goods suppliers

http://www.learncheme.com/simulations Interactive simulations for Chemical Engineering

http://www.wolframalpha.com/ Dictionary / encyclopedia
http://patrickjmt.com/  maths video lessons

http://www.eevblog.com/  video resources for electronics

http://www.calculator.org/calculate-online/calculators.aspx  online tools (Calculators)

 

interactive simulations

https://phet.colorado.edu/

http://www.myphysicslab.com/

http://www.physicslessons.com

http://www.edumedia-sciences.com

http://www.falstad.com/mathphysics.html

http://www.learncheme.com/virtual-laboratories

 

http://www.engineergirl.org/144.aspx for school students

http://www.egfi-k12.org/whats-new/e-tube/ for school students