Wolfram Research
Wolfram Math World: Hyperboloid
This Math World site explains how the hyperboloid is created from a hyperbola, illustrated with graphs. The site then goes into detail giving the parametric and cartesian equations for a one sheeted hyperboloid and then the two sheeted...
Wikimedia
Wikipedia: Hyperboloid
A basic definition is given for what a hyperboloid is and the equations are given for a hyperboloid of one and two sheets.