an open Source visualization software with several graph layout programs.
VTK (The Visualization Toolkit)
an open source visualization program for 3D computer graphics and imaging.
an open source interactive graph visualization platform that runs on Windows, Linux and Mac OS—accepted again by Google Summer of Code 2011.
CiteSeer is a scientific literature digital library and search engine that focuses primarily on the literature in computer and information science. CiteSeerx aims to improve the dissemination of scientific literature and to provide improvements in functionality, usability, availability, cost, comprehensiveness, efficiency, and timeliness in the access of scientific and scholarly knowledge. CiteSeerx has developed new methods and algorithms to index PostScript and PDF research articles on the web.
arXiv.org provides open access to 668,955 e-preprints in Physics, Mathematics, Computer Science, Quantitative Biology, Quantitative Finance and Statistics.
Numerical Recipes Online provides online access to Numerical Recipes books in C++, Fortran 77 and Fortran 90, and more. These titles are publicly available, although some have printing limits.
Here are some Virtual Laboratories for hands-on learning:
CS50 (Stanford University)
Discovering Computer Networks – The Open University
DevNet Learning Labs - Cisco
F5 Training Programs and Online Classes - F5 Networks
VMware Hands-On Labs
VMware NSX Hands-on Labs for Free
Juniper Networks Virtual Lab Services
Nvidia Cumulus in the Cloud
NDG Online and NETLAB+
Hands-On Labs in Google Cloud for Networking Engineers
18 Network Simulation Software Tools for Certification Practice or Research