B&B vendors are a good place to start and have some of the best prices. Gary and Archerfire come to mind. If they don't have what you are looking for, Surrender to Chance has been my go to for a while now. The Perfumed Court is also an option, but typically pricier and slower to ship. Lucky Scent also sells samples of most of their scents, but the samples are small and do not come with an atomizer.
As a start, go to the vendor section of B&B here and look for Archerfire Decants and Garry's Sample Shop and check them out. Other sites outside of B&B selling decants/samples include:
Luckyscent.com
Decantshop.com
Surrendertochance.com
Theperfumedcourt.com
Theposhpeasant.com
Thanks everyone. I have looked at Gary's for the shaving cream/soap samples. I guess I have never looked farther down the post. Now I feel a bit silly...
To the above I would add the manufacturer depending on what brand you are after. Geo F Trumper and Truefitt & Hill sell samples. TOBS samples used to be available on The Shave Den. Others may; got some from Floris by asking nicely.