h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I like the idea of having guide entries for all the chemical elements, and therefore I encourage you to excel at this task. The story of the discovery of the chemical elements makes fascinating reading. If you can find "The Chemical Elements" by Helen Miles Davis, that would be a good start.

Some interesting things about Helium you might want to include are that it is the first element which was discovered outside of the earth before it was isolated on earth. Helium was first suspected as being a new element in 1886 by spectroscopic examination of the emission spectrum of the sun's corona which was obtained during the solar eclipse in India in 1868. Frankland and Lockyer suggested the name Helium from the classical greek Helios, the sun god. It was later discovered in terrestrial ore samples by Sir William Ramsay in 1894, although now I believe that most commercial sources are extracted as part of gas and oil drilling.

Helium, when cooled below its liquification point, undergoes a transition from a normal fluid to a "superfluid", capable of creeping up and over the edge of it's container. The discovery of and understanding of this and other properties of helium II were milestones in the development of quantum physics.

You can probably find many more interesting items on this element.