(702) 990-3210 phone
Central Casting, for better or worse (worse includes lost hours and work as background come in from LA to work here in the Nevada local) has a presence, so registration with Central Casting in LA is recommended. Despite claims of roles, Central Casting is primarily (by far) a background casting house).
Please provide corrections and additions, as this list was compiled in 2009. As you know companies come and go in this industry.
Please provide additional companies and links as you become aware of them. Your help is appreciated. Note that casting companies are hired by and represent production companies / management. They are not agents or talent managers. Their job is to find the right people for the job, make sure they do the job and save the production company money when possible.