Check out Trillian ->
http://www.ceruleanstudios.com/downloads/ out of the box you can contact to ICQ, MSN, Yahoo, AIM and IRC but I think there is a Plugin for GTalk as well (tho Plugins can only be used by Pro Users, not that much money at around $30).
One of the features I really like is to create "MetaContacts" where you group the various Messenger contacts of the same person. Eases up on a lot of clutter.