The B&H website's film section is pretty complete as far as the major manufacturers go.
Freestyle's website and fotoimpex cover the East European films fairly well.
Japan Exposures includes Fuji products for the Japanese market not easily available otherwise.
Badger Graphics sometimes has special orders for sheet film that isn't widely carried, like 5x7" transparency.
Lomography has its own branded films, most of which are available through other channels under other names.
That's most of it.
Not sure where to find up to date information on Chinese film. Ferrania--they still around?