Well I have this lava rock leftover from a CL purchase. His tank wasn't the cleanest and it's been dry for about 2 months now. I went to go clean it off and it has a weird smell to it. I don't know how to describe it, it doesn't smell bad but it's just odd. I figured because it's lava rock and has so many small holes in it I should give it a thorough cleaning. Which means using salt.
For rocks / driftwood just boil them for a bit the let them dry out, no need to use salt at all.
On the mater of table salt, You can use non Iodized table salt without any additives in a fish tank as a substitute for aquarium salt. I've used it to help with the healing of minor wounds on fish before.