Kombucha seems to be the new "it" drink (although I live in the Bay Area, so this info may be biased). Of doubtful origin, this fermented tea has a passionate following who claim all manner of health benefits for it. I just like it because it tastes good.
Step 1: Obtain Kombucha Starter
You can buy the yeasty starter on the web (sometimes misidentified as a mushroom), or get it from a friend. You might also try looking on message boards of health food stores.
The starter replicates itself in each batch, so one is enough for your lifetime. Soon you'll have enough for everyone you know!
Step 2: Make Sun Tea
Add two to five tea bags (black or green) to three quarts of water. Let it steep for 8-24 hours, depending on how black you like it.
Step 3: Add Sugar
Add 1 cup of sugar to the water (the starter feeds on sugar, so the final drink will not be as sweet as the original).
Step 4: Stir Well
Like I said, stir well until all the sugar is dissolved.
Step 5: Add Kombucha Starter
Add the starter to your tea, along with any remaining liquid from the last batch of kombucha.
Step 6: Cover and Store
Cover with a clean tea or paper towel and seal around the rim with a rubber band. Store in a spot out of direct sunlight for 7-14 days (depending on who you talk to).
When its time is up, start all over again! Your starter will have grown another layer, which you can peel off and use for a second batch (or give to someone else).