I'll try to come up with as many titles as I can but please add any that you may think are pertinent/relevent to the topic.
Ok, first off is the MadMax/RoadWarrior trilogy - an absolute must see is MadMaxII just to get a real insight into what wandering the wastelands could be like.
A Boy and his Dog - an interesting take on a wastelander suvivor who comes into contact with a bunch of people living in an underground bunker system
The Omega Man/I am Legend - The Charlton Heston version was the best IMO
Tank Girl - a silly film but worth a look
Jericho the TV series
Cherry 2000 - B grade again but still worth a viewing
The Stand tv mini series
Damnation Alley
On the Beach
DeathRace 2000 [1975 version]
Planet of the Apes
Threads
The Aftermath
and to wind up, A Blast from the Past - a cute film that really has the retro feel of the late 1950's/early 60's to it. Although a nuclear war didn't happen it's still amusing to watch.