I've used the Feliway for my cats in the past and it's worked OK - depending on what it's needed for. Another product I've used is Valerian based Pet Remedy which is also a diffuser. BUT... this one you can smell as it is a regular herb. Personally I don't mind the smell of it but I know it makes some people nearly gag http://www.petremedy.co.uk/
Also, another thing worth trying Kaz is Bach Rescue Remedy... about 8 drops into the palm of your hands, gently rub them together and then rub their ears (it's where the skin is the thinnest so absorbed better) or about 10 drops a day into their drinking water. http://www.bachflower.com/rescue-remedy ... ch-flower/