Well I think

Porsche- Cayman S thread
Pontiac- Solstice, G6 Coupe/Cabrio threads
Land Rover- LR3 thread
Mercedes- B class, Get rid of "CLR" and "Vison SLA", CLS class, R class, AMG threads
Mercury- Mariner thread
Lincoln- change "Blackwood" to "Mark LT/Blackwood" threads
Jeep- Commander, concept threads
Cadillac- V Power thread
Chevrolet- SSR thread
GMC- Denali line thread
Bentley- Continental Flying Spur, Dominator threads
BMW- M thread
Cars in General- spy photo thread
Saturn- Sky thread

Hummer forum
Maybach forum
Smart forum

I also think there should be a forum about aircraft (gliders, prop planes, jets, etc.)

Watercraft (boats, jet ski's, etc.)

ATV's, snowmobiles, go-karts, bicycles all under the motorcycle forum

RV's/ Trailers

small engines

and other machienes that have engines, but arent cars