The following is a simple shell script using the KDE dcop client to open new tabs in konqueror (or a new instance of konqueror if it's not running). I use this from pine's url-viewers setting to launch new tabs with a url contained in a email.

#!/bin/sh

KONQ_WIN=`dcop konq* | head -1`

if [ "$KONQ_WIN" = "" ]; then
    /usr/local/bin/konqueror $1 &
else
    NEW_TAB=`dcop $KONQ_WIN konqueror-mainwindow#1 action newtab`
    dcop $NEW_TAB activate
    dcop $KONQ_WIN konqueror-mainwindow#1 openURL $1
fi
return 0