Logos.com is undoubtedly the heavyweight among all of the sites featured in this section. It contains the greatest wealth of resources that you can wield to make your study comprehensive and complete. It also has the ability to link across several of your connected devices so that your phone or tablet can keep up with the study you are working on at home on your desktop.
However, logos.com is not completely free. You can complete a formidable study with logos.com without paying, but the more advanced features (which you may never need) will cost. This video tutorial will help, but if you're interested in using this site, you should either just dive in and experience it, or seek other tutorials to augment this one.
https://www.youtube.com/watch?v=H6bZWVUmCS8