MathnetBase
http://www.mathnetbase.com/
   --over 160 volumes currently online
   --comprehensive coverage from pure mathematics to applications in finance, biology, engineering, and more
   --tips, techniques, and tutorials for MATLAB, Java, and other sofware tools
   --tens of thousands of pages of equations, facts, figures, models, theories, and expert guidance, constantly growing with new content

PhysicsnetBase
http://www.physicsnetbase.com/
   --up-to-date theory, historical accounts, and profiles of our favorite physicists throughout the ages
   --explorations at scales ranging from subatomic to astronomical
   --research findings, commentaries
   --over 205 volumes currently online

StatsnetBase
http://www.statsnetbase.com/
   --theory, research results, and applications for implementing a variety of statistical analyses and methods
   --statistical tools and approaches applied to such fields as finance, biology, engineering, and manufacturing
   --expert guidance on software environments, including several books devoted to R
   --over 120 volumes currently online

... more trials ...