February 9th 2009 The first major firmware update for the Nokia 5800
http://www.allaboutsymbian.com/news/item/8920_Nokia_5800_firmware_update_to_.php
Probably the easiest way of updating the 5800's firmware is to use the OTA ("Over The Air") method. the 5800 supports User Data Preservation, which basically means your own settings and data are left untouched during the update process. However, it's still a good idea to back them up before the update just to be on the safe side.
http://www.allaboutsymbian.com/features/item/How_to_update_the_firmware_on_the_Nokia_5800_XpressMusic.php
5800 forum
http://ubuntuforums.org/archive/index.php/t-1049778.html
http://mobile.yahoo.com/