Crème fraîche is a dairy product that is similar to sour cream, but it is not as thick or tangy. If you prefer something a little milder, then crème fraîche is the way to go. However, it is not readily available in some some places. I usually get a blank stare from the guy in the dairy department when I ask if they have it, as he normally has no clue what it is.
Fortunately you can make it at home using two simple ingredients that the dairy guy will know about: heavy cream, and buttermilk. Heavy cream is about 35% butter fat, and is also known as whipping cream. Regular cream for coffee will not do the trick.. Buttermilk, by contrast, is quite low in fat (it is the liquid left over when butter is churned, so the fat has been mostly removed.)
All you need to do is add a small amount of buttermilk to a cup or so of heavy cream, and allow it to stand at room temperature (covered) to allow the cultures in the buttermilk to work on it. The longer it sits at this temperature, the thicker it will become.
Crème fraîche is great on anything that would normally call for sour cream, but would benefit from a milder taste. I particularly like it on potato pancakes, in my butternut squash soup recipe, or even with some chopped herbs as a dip.
It can also be whipped, and is better for cooking at higher temperatures because of the higher fat content. And it's so easy to make!