SIM (Simple Instant Messenger) is an unpretentious ICQ client which supports
many of the features of Version 8 of the ICQ protocol (ICQ 2001).
(QT is needed, can be build for KDE).

Special Features

    * sending and receiving SMS
    * server-side contact lists
    * phone directories
    * file transfers
    * chat
    * user search
    * proxy support (SOCKS4, SOCKS5, HTTP)
    * a SPAM filter
    * secure direct connections with SIM and Licq
    * message or chat mode for the user window
    * keyboard shortcuts
    * message forwarding

WWW: http://sim-icq.sourceforge.net/