It looks like most of the different logging cars have been mentioned here, so I'll just put in a summary list, or whatever you want to call it.
Disconnect log cars (available with logs or as separate trucks)
Skeleton log car (I have 3, and they're absolutely excellent)
Truss Type log car
Logging caboose (very nice little car. Could be used as a "tool car")
ACF 40' log car (1906-1935)
ACF 40' log car (1935-1960)
Skeleton log cars (sold in pairs, out of production, still available in some places)
Truss type? log car (25' or so in length. Decent model, but needs better trucks. Out of production)
Climax log car (adjustable length. Doesn't include trucks, coupler, or logs)
Logging caboose (modeled after a Grasse River caboose, which was rebuilt a lot over the years. Doesn't include couplers)
I think those are all the major brands of log cars. The Kadee cars all come as unpainted kits, but they're excellent quality and make very nice models when finished. The Keystone cars are also kits, and they appear to be pretty good quality too. The rest of the brands are ready to run.