Nature has a news blurb about the isolation of a still-infectious viral particle from 30,000 year-old Siberian Permafrost. The story started with the 2012 report of the recovery of a blooming plant, which was germinated from fruits which had been cached in burrows by ancient squirrels. Researchers in France contacted the Russian field scientists and obtained soil samples from the same dig. The French team was interested in giant viruses, a recently discovered class which infects amoebas. So they basically exposed amoebas to the soil samples- and indeed, some samples contained a pathogen which killed the amoebas.
The new virus is named Pithovirus sibericum, and like other giant viruses, its genome is handled in an almost microbial fashion, with the large DNA genome not compacted, as in more familiar viruses. The DNA sequences have yielded lots of unknown sequences potentially encoding genes. It will be interesting to see how these viruses relate to the rest of the viral world, especially if there would be hints of another kingdom of life.