FlavourArt: Food Flavoring. Very wide selection of flavorings. Not as concentrated as Lorann, but has a wider variety of flavoring and less artificial coloring. Variety of Tobacco flavorings.
Freedomsmokeusa and liberty flights both carry a very good selection of FlavourArt flavorings.
Freedomsmokeusa
:Liberty-Flights
Decadent Vapors/Totally Wicked: The Decadent vapor line is produced in the UK.
Decadent Vapors
There are other products and suppliers out there. These are just the ones I use most often and am familiar with.
Schilling and Mccormick flavorings will also work--they are just not as concentrated.