Can spiders smell?

Answer 1

yes, they can. even though they have 8 eyes, their vision kind of sucks, so they rely on smelling.
http://findarticles.com/p/articles/mi_m0EPG/is_n7_v29/ai_17027826

Answer 2

Some spiders have been shown to detect pheromones, and the possibility is likely there for more, but the odds are thhat they work more by vibration. If you want to find out more about this sort of thing, the good (and I think only) spider book is by Dr. Rainer F. Foelix. It's well worth the money. There is an old book by JH Comstock called The Spider Book which has a lot of good information, but the names may be a bit out of date.