Kefir is a cultured milk product, similar to yogurt. It contains healthy bacteria along with all the goodness of milk (protein, calcium, etc.). I first heard of kefir 3-4 years ago, when a friend decsribed it to me and gave me some of her extra "kefir grains" -- the culture used to make kefir.
At the time, I didn't particularly care for the taste of plain kefir (it's very similar to the taste of plain yogurt) but loved adding it to smoothies! I've also made kefir pancakes, and kefir can be substituted for buttermilk in many recipes.
With the busyness of baby #3 (Ruth), I stopped making kefir for a while. Six months ago, I got some fresh kefir grains and started making kefir again. The children are older now (ages 6, 5, 3, & 1 rather than 3 &2!) and have been helping me consume the kefir with no problem!
Why I love making kefir:
It's healthy. (Better than drinking plain milk!)
It's affordable: a one-time cost to purchase the culture, called "grains", and then the only expense is milk. Even better, find a friend who makes kefir and is willing to share the extra grains. (Or start your own, and be that friend for others.)
It's super, super easy. It's probably the easiest thing I do in the kitchen! :)
I asked Yehoshua (6) to take a video of me one day when I was ready to "make kefir". As you will see, it took just a couple minutes. I love Yehoshua's enthusiasm when I am describing how one can eat kefir and he chimes in with his favorite ways to eat it. ;)
To make kefir, you need the culture ("kefir grains", pictured above) and some milk. I use regular whole milk from the store, but you can of course use organic milk, raw milk, etc. A tablespoon of kefir grains will make a cup of kefir daily, and the grains will grow fairly quickly, so you'll soon be making as much kefir as you could ever wish for -- and have grains to give away to friends! :)
Add some milk (cold, from the fridge is just fine!) and allow the milk + kefir grains to sit at room temperature for 24-48 hours. The result is what you see in the video above: thick, creamy kefir! Remove the grains, add fresh milk, and wait another 24 hours for more kefir! :)
These are the same grains as the photos above -- 8 days later, you can see the grains have probably grown by about 50%.
More about kefir:
Podcast about how I started making kefir (4 minutes, mp3)