I've had good luck with B&H, KEH, Calumet, Alkit, and Pacific Rim Camera. I order just about all of my B&W film from J&C and can't say enough good things about them!

I had one issue with an order from Calumet - they sent the wrong part once, but one phone call was all it took to resolve the problem. To be fair, the wrong part that they sent was actually in the correct box for the item I ordered, so it was really a manufacturers problem (Metz).