Here is an interesting article from the September 2009 Backpacker Magazine written by Steve Howe.
How to Start a Fire With Fungus
Chaga, or "tinder fungus" and other natural
firestarters abound in the backcountry–you just have to know where to look for
them.
Commercial tinder, petroleum jelly-covered cotton balls, and
dryer lint are all great for starting a blaze–until you realize you left them
at home. But lucky for forgetful hikers, the woods are full of natural
firestarters. One of the best: chaga, aka tinder fungus. This chunky black
mushroom ignites easily, smolders for hours, and emits a pleasant, woodsy
smell. Here's how to use it.
Find it
Chaga fungus grows year-round in cool northern forests from New
England to the Northwoods of Minnesota and Wisconsin
and into the southern Appalachians. Look for it on birch
trunks; the dark, bulging mushroom resembles burnt charcoal and often sprouts
up where the tree has been injured (chaga is a parasite; you won't become an
LNT outlaw by taking a small chunk). Pry a palm-size piece of the fungus off of
the trunk with your multitool.
Light it
Flint Scrape any part of your fungus chunk with a knife to
produce a pile of powder, then direct sparks directly onto the pile. You can
also place the fungus on the ground, off the edge of your flint or fire
striker, and let the sparks land right on it. The highly flammable chaga will
ignite no matter which method you choose.
Lighter
Simply hold the entire chunk to a flame.
Adapted from Born to Explore: How to Be a Backyard
Adventurer, by Richard Wiese ($19, HarperCollins)