Hybridization

Simply considering the valence orbitals without hybridization and placing them all on one axis is not very helpful in describing the geometries compounds adopt. Pauling's theory of hybridzation allowed mixing of the s and p orbitals to form orbtials of mixed character.

One s orbital + three p orbitals

Taken from http://www.headroyce.org/~sglogover/Resources/Resources.html

One s orbital + two p orbitals (one p orbital left over)

Taken from http://library.tedankara.k12.tr/chemistry/vol3/Hybridization%20in%20molecules%20containing%20multi%20bonds/z87.htm

One s orbital +  one p orbital (two p orbitals left over)

Taken from http://wps.prenhall.com/wps/media/objects/724/741576/chapter_01.html