There are a few great sites that compare methods for recording the ambience of a place (or soundscapes) and for making your own mics. It is amazing what can be made for very little investment (excluding time).
frogloggers mic capsule suppliers and helpful customer service with technical background.
Library of animal calls, buy cialis software & related research:
Wildlife Acoustics for remote/automated recorders (and related research links page).
Check out the Nature SoundMap project: listen to the sounds from around the world! I am delighted to have my recording of an American Bittern from the Purdon Conservation Area (near Ottawa) included.
More soundscapes of the Earth Wildlife Sanctuary with Bernie Krause.