Free! MACAULEY LIBRARY at the Cornell Lab of Ornithology is "the world's largest and oldest scientific archive of biodiversity audio and video recordings." The entire collection is quite overwhelming -- we didn't know where to start or finish in the vast taxonomy -- but extremely engaging for the geeky at heart or the ornithologically-inclined. Here are a couple of hot tips: For the standard intro to biology class sans the yucky parts, start in the Chordata region of the taxonomy. And if you're deathly afraid of spiders and other creepy crawlers, avoid the Arthropods!
