I wrote about the online library of birch bark letters before (here and here). A good news: the full archive will be translated into English. A large part of the birch bark writings is already translated. The publication of the English texts is scheduled for early 2008.
Currently, the online catalog includes 1,049 inscriptions dated by XI-XV centuries and found in Veliky Novgorod, Vitebsk, Zvenigorod, Staraya Russa, Tver, Torzhok and other locations.