Plants Vs. Zombies and the PSone Classic versions of the first three Resident Evil games. Altered Beast will also be available for free. Yeah, we know it's not a zombie game per se, but the protagonists do wise from their gwaves.
Discounts are also headlined by Resident Evil titles, as the HD debut both Resident Evil 4 and Code: Veronica X will be half-price for PlayStation Plus subscribers. Head over to PlayStation Blog for the full rundown on all the offers in September.