Researchers at PennState have published the DNA sequence of an extinct Woolly Mammoth; see the news article at Nature.com, or the November 20, 2008 issue of Nature for a paper by Miller, et al. (Nature 456, 387-390: “Sequencing the nuclear genome of the extinct woolly mammoth“).
Mammoths went extinct some 10,000 years ago, but have been found preserved in Russian permafrost. The hair from one of these preserved (mummified) ancient beasts was used to retrieve DNA. Hair is useful for such extractions as it is relatively easy to wash away contaminating (foreign) DNA.
One tidbit that I found quite interesting: where did the researchers get the Mammoth hair? They bought the hair on Ebay.com! You can too, for only $175.00 for 2.5 grams. Yes, the researchers did verify that this was actual mammoth hair. Anyway, the big question is whether or not we will shortly have a Mammoth clone. Short answer: not any time soon. This is just the first step, but is a major one.
Our ancestors did see live woolly mammoths; here’s a cave painting in France depicting one: