The interactive periodic table
Here's yet another reason we're certain that we were born too early.
High school chemistry would have been a lot easier to study with the aid of this interactive periodic table, which offers all manner of information about the elements obtained simply by mousing over the panels. Clicking on them gets you definitions and other information from Wikipedia.
Even more impressive is the Standard Electron Orbital Configuration, which includes interactive graphics and other data that look important and useful--though, to be completely honest, we have no idea how to read them. (OK, we admit it: We still would have flunked our 11th grade chem class.)