I've always wondered if you could make sour cream yourself. We go through so much of it here with potatoes and a lot of Mexican cooking. Here's a recipe I've found, but I haven't tried it yet. I'm thinking that in order for it to be cost effective, you'd probably need your own cow or goat.
2 cups light cream
2 T. light buttermilk
Combine in a hot glass jar, canning jar. Cover and shake gently to mix. Let stand in a warm place for 24-48 hours until thickened. Store in the refrigerator. This keeps up to three weeks.
From Glory Farm