Movies are not the only places to find these teams. Some people create them out of love for the undead. Some create teams to prepare for any possible outbreaks in areas susceptible to them. Others make teams for an atmospheric RP (roleplay). These particular RP sites can be found online; Myspace is a major RP site and has many different types of zombie RP pages.
The cast of "Resident Evil" counts as having a team. Recently, in their latest movie release called "Resident Evil Degeneration", the S.R.T -- or Special Resource Team -- are organized groups that are normally found to be the first responders to a zombie outbreak.
If you wish to join Team Z.E.S.S.T (The Zombie Encounter Strike and Survival Team), members are currently being recruited. Visit zombieencounter.com to join!