Right of the top of my head...
Indian Creek
Pure Gold
Truglo
Comp-N-Choke (Also makes Kicks)
Trulock
Carlson
Briley
Rhino
SumToy
Jebs
Hastings (No Longer Manufacturing)
Wrights (Swarm)
Colonial Arms
Seminole Gun Works
Walkers (Wad Wizard)
Primos (Not sure who makes them)
Patternmaster (Not sure if this is the actual name of Manufacturer)
Then of course you have all the firearm manufacturers that provide choke tubes with shotguns. I can't tell you if they actually manufacturer there on chokes however.