http://www.earlham.edu/~peters/knotlink.htm
http://www.tcm.phy.cam.ac.uk/~ym101/tie/aps97tie.html
On his Web page Knots on the Web, philosopher Peter Suber of Earlham College in Richmond, Indiana, has gathered together a host of Internet resources on the mathematics, tying, history, and art of knots. If you’re interested in the theory behind one particular kind of knot—the kind that holds neckties in place—then visit Theory of Tie Knots, a site created by physicists Thomas Fink and Yong Mao of the University of Cambridge.

http://www.ucar.edu/40th/webweather/
From the University Corporation for Atmospheric Research in Boulder, Colorado, comes Web Weather for Kids, a Web site devoted to teaching children about the physical processes behind the weather. In addition to providing tutorials on such topics as thunder and lightning, the site describes simple experiments that can be done at home or in the classroom.

http://ranier.oact.hq.nasa.gov/telerobotics_page/coolrobots.html
Every week, members of NASA’s Space Telerobotics Program bestow the title Cool Robot of the Week on a robot and its associated Web site. Recent cool robots have included Troody, a bipedal walking dinosaur robot, and Nomad, a four-wheeled robot that roams Antarctica in search of meteorites.