I was reading a graphic-design blog and came across a comment on how recognizable the smell of Crayola crayons is to American adults (very).  In consequence, I thought about what smells I found were so identifiable that they practically screamed what they were, and I came up with:

Coffee (studies have shown that the smell of coffee can increase appetite, even in those satiated or aversive to food)
Laundry soap/ the dryer
Crayons
Play-doh
Industrial cleaner, mostly ammonia
Photocopier/ printer
Old book
Copper/ really any metal that makes your skin smell/ coins
Sunscreen
Baby powder
Batik wax
Nail polish
Toast
Peppermint

Thoughts?