Heard a rumor through the Association of Moving Image Archivists (AMIA) listserve that a 1926 John Gilbert film, Bardelys the Magnificent (an historical drama set against 17th century France and directed by King Vidor), has recently been discovered. This film is listed as one of the most wanted silents on silentera.com's website.
Additionally, Silentera.com has a link at the top of their site homepage to a very curious exchange that appeared on Criterion's Forum blog. Apparently a copy of the much sought-after film Four Devils (1929) might exist. This was F. W. Murnau's follow-up to Sunrise (which is often cited as the greatest silent film of all time). The film is about a trapeze act, two of whose members fall in love (played by Janet Gaynor and Charles Morton) but who are torn apart by the entrance of a "vamp" who tempts the male away (played by Mary Duncan)
A 1928 novelization of the film offers several stills (two I've posted here), which don't necessarily strike me as making for the best film (nor does the film's plot); however the historical value of the film alone would make it one of the film finds of the decade.