feliway is a synthetic 'feel good' hormone for cats. its imitates the phereamones the cats leave places when they rub their cheeks and scent mark (does that make sense?)
try ebay or just google it. can also be found in most vets or pet shops.
This is the link where you can buy it, and find some info about it. I would just suggest searching the net for more info. I got mine from www.petguys.com (the cheapest one i found)
AND I LOVE IT!!! Comfort zone ROCKS! I have had such great experiences from this product. Its unbelievable. I would recommend it to ANYONE with any cat in thier house. It is great! I would love to stay and talk about it, but I've got much to do. But i suggest, getting it. for whatever reason.
I must admit we tried it for 3 months and found that it did not have any noticable effect. It was a rather expensive failure. I know it works for others tho.