Empathy is the default messaging program replacing Ekiga in Ubuntu from 9.10 relesase, supporting text, voice, and video chat and file transfers for many different protocols. This allows one application to deal all your accounts and IRC chats.
Default Settings Locations
~/.mission-control/accounts/accounts.cfg (except passwords which are stored in gnome-keyring).
Logs (since Empathy 2.31.4):
Logs (up to version 2.31.3):