It is very possible that you can share good milk (and other) cultures with someone in your community, but if that is just not possible, then the best thing is probably to order some. I have never used these sites, but am listing them for your convenience.
For the most part, I just try to buy a sample of whatever I am making. Julie just let me know that they have creme fraiche at Save Mart, so I will go buy some and use it for my starter. I am looking forward to making some with the raw Organic Dairy cream and using it in various ways. I love to try new things. :) :) :)
Kefir Lady (also lists benefits for kefir)
Also, here are a few sites for cultured milk products and their benefits. Hope there are not a bunch of pop up ads. Those are really annoying :(
And a thesauraus of cultured milk products..... gotta love google :)
Cook's Thesaurus: Cultured Milk
Best of Health