The Times reports that a poem by Lord Byron has been discovered in a 19th-century book within the archives of University College London. It turns out that it was stumbled upon by a librarian whilst doing some routine cataloguing.
Libraries seem to have a knack of uncovering "lost" works. Here's a list of other recently unearthed works:
December 2005: A 17th century painted female figure was discovered under 20 layers of paint in the in the King's Library at Kew Palace, London.
April 2005: 28 lost omnibus recordings of The Archers from 1977 were discovered in the archives of the gramophone library at BBC Radio Wiltshire.
August 2004: A "lost" essay by Virginia Woolf about London life in the 1930 was discovered in the archives of University of Sussex's library.
September 2003: A "lost" play by Agatha Christie was discovered by her grandson more than 70 years after it was written in the vaults of the British Library.
July 2003: Lost songs of Piaf were discovered in archives of the national library in Paris.
December 2002: A manuscript by JRR Tolkien, thought to be his last work, was discovered in an Oxford library.