Interesying article featuring scented stamps:

In the last 35 years, there has been a growing number of scented stamps being issued. From the first smelly stamp through to the most current olfactory offering, the use of scented stamps are a novelty that are becoming more and more prevalent.

Here, then, is a list of some of the more notorious scented postage stamps available for collectors. Every stamp is valid postage in the country it was issued.
Read the full article here:
The World's Smelliest Postage Stamps