EBSCOhost multi-disciplinary database for academic publications, since 1975, including peer-reviewed journals, and images. For mobile access, download the EBSCO app
The name says it all - brief, easy-to-understand explanations of how just about anything in modern life works. You can search by keyword or browse by category. There is a free email newsletter
PhysLink.com is a comprehensive physics and astronomy online education, research and reference web site. In addition to its search feature, it has good links in its education and reference section