Kombucha

We have been making and drinking our own kombucha for a couple of years now. It is an easy, inexpensive, yummy, and refreshing way to enjoy some probiotics. I purchased my first culture, called a SCOBY (symbiotic culture of bacteria and yeast) online, but have made multiple ones on my own since then from bottled GT Dave's kombucha (which has currently been taken off the market for too high alcohol content/labeling issues). Here's what we do:

Kombucha
3/4 c. cane sugar (any kind - honey also works although some sources say it doesn't)
3 quarts of water
2 or 3 quart-sized tea bags (must be caffeinated)
SCOBY
1/2c. kombucha or distilled vinegar

Bring water and sugar to a boil, and boil for 1 minute. Remove from heat, and steep tea bags ~10 minutes. Remove tea bags, cover sweet tea with a clean cloth, and cool to room temperature. Rinse a 1-gallon glass jar with distilled vinegar, and place SCOBY and either 1/2c. kombucha (from a previos batch) or distilled vinegar into jar. Pour cooled tea into jar, and cover with a clean cloth held tight with a rubber band. (Be sure that your cloth is a tight weave that will not allow fruit flies to enter.) Place in a dark area and check every few days to see if kombucha is growing a new layer of SCOBY and to see if it has reached a desired sourness.

When it is ready (a totally subjective call you will have to make), we chill our kombucha. It is quite a refreshing drink - especially on a hot day. We generally pour it into clean glass jars, but we have also experimented with bottling it in recycled kombucha bottles and in capped beer bottles. Both these have worked well, and you can get a bit of carbonation if you bottle it when there is still some sugar left in the tea or if you prime it with a bit more sugar or fruit juice before bottling. The trick is not to add some much sugar that the bottles explode :o).

You can grow your own SCOBY, a gelatinous culture that grows thin and flat about as wide as your jar, from ready-made kombucha very easily: I make a smaller batch of the tea and add the kombucha. Generally, I start with 1 quart of tea and 1-2c. of kombucha. Then you wait until you see a very thin, new SCOBY form. I take that SCOBY and some of the kombucha to make another batch, and then scale it up, ~ doubling each time to eventually get to the size I want.
I generally just pour the SCOBY from one jar to the next or often use the same jar again and again, pouring most of old batch into a fresh jar and adding the new tea to the layers of SCOBYs already there.
Eventually, you get quite a stack of SCOBYs, and you'll want to remove all but the newest and start fresh. You can keep only the newest one each time, but I'm just too lazy. When you go to separate the SCOBYs, wash your hands, and then rinse them well with distilled vinegar (and hope you don't have any little cuts on your hands because they will STING!). Then gently peel the newest SCOBY off, and put it into a vinegar-rinsed jar. You can compost your old SCOBYs, feed them to your chickens if you're lucky enough to have some, give them to a friend, or just throw them away. They can also be sent through the domestic mail; just include enough of the kombucha to keep the SCOBY moist, and double bag it in clean ziplock bags.
You can rest your SCOBY by placing it in a jar in the refrigerator. Make sure it is covered with kombucha, and place a lid lightly over the jar so that the SCOBY can breathe. They can be left a couple of months, but may not be as vigorous when you first bring them back from vacation.
There are numerous mail-order businesses that will sell you SCOBYs (here's a page with some in NZ) if you can't find any commercial kombucha for starting your own.