ICQ vs Pidgin
ICQ is an instant messaging computer program. ICQ features include sending text messages, offline support, multi-user chats, free daily-limited SMS sending, resumable file transfers, greeting cards, multiplayer games and a searchable user directory.
Pidgin (formerly named Gaim) is a multi-platform instant messaging client. It provides the ability to have voice/video conversations using the XMPP protocol (including Google Talk). Further features include support for themes, emoticons, spell checking, and notification area integration.