I think the land boom around the Salton Sea done busted along with the rest of the housing boom, so I bet a lot of that boxlike housing is vacant now (or was platted but never built out). I haven't been out there lately to check, though. But a lot of the "future that never happened" architecture is gone, true.
Bombay Beach is a weird little place any way you look at it and should still have some abandoned sections. The northeast corner of the Sea in general has some interesting stuff; North Shore is a tiny little settlement that when I was last there seemed to sort of be a failed attempt at suburbia, and the International Banana Museum was supposed to open there in January 2011, which isn't exactly "ruined/abandoned" but about as odd as you can get.
Sightseeing on Google Maps is actually a pretty good way to discover interesting things out there. Just be careful; not everything shown as a road is passable.