I do a private dinner club at my place once a month and have been trying to compile a nice list of places to source different proteins and ingredients online. Please feel free to add your favorites and experiences and I'll update this as I go along as well.
Heritage Foods USA (NY) - great customer service and my favorite go to for pork products.
Niman Ranch - Haven't used them personally yet but I have heard good things about their products.
Hudson Valley Foie Gras (NY) - probably the best place for great quality foie that i've experienced
Gourmet Food Store (Various sources) - very wide selection of foods categorized by region. It's more of an online market so quality and price varies.
U.S. Wellness Meats (MO) - decent selection of grass fed beef.
Dartagnan- pretty common name in gourmet food these days. Good for duck products and game birds.