Filamentality
Filamentality is a fill-in-the-blank interactive Web site that guides you through picking a topic, searching the Web, gathering good Internet sites, and turning Web resources into learning activities. It helps combine the "filaments" of the Web with a learner's "mentality". Support is built-in through Mentality Tips that guide you along the way to creating a Web-based activity you can share with others even if you don't know anything about HTML, Web servers, or all that www-dot stuff.
http://www.kn.pacbell.com/wired/fil/ 

Virtual Simulations of Microscopy and Optics - Make sure you check out the Polarized Light Microscopy to see how crystallized specimens appear when viewed through a polarized light microscope. Samples include a Moon rock, a dinosaur bone, spinach, amethyst and many others.
http://micro.magnet.fsu.edu/optics/tutorials/index.html