It's TEOTWAWKI and I'm offering 3 for 1 on two series...

Sword of the Spirits Trilogy  by John Christopher.  The adventures and rise to/fall from power of young Luke in a post-apocalyptic world that has returned to medieval times.  Order the first book (Prince in Waiting) and get the third book (Sword of the Spirits) and the unpostable second book (Beyond the Burning Lands) free.  

Stormrider Trilogy by Robert Baron --  Follows the fortunes of Tristan, the last of the HardRiders, through a post-apocalyptic world where biker gangs travel the countryside and war with the repressed, civilized Cities.  It is very similiar to the Mad Max/Road Warrior movies, but also, alot like a western where indians are at war with the cavalry.  Order the first book and get the second and third books free.

Update:  Sword of the Spirits has been taken.