ok
ftp.slackware.com/pub/slackware/slackware-current/
is the main site, or use a mirror depending where you are. I am in the UK and use
ftp.heanet.ie/mirrors/ftp.slackware.com/pub/slackware/slackware-current/
which is always really fast.
go to .../slackware/slackware-current/slackware/kde/ and you will find the packages
I have the following installed:
kde-i18n-en_GB-3.5.1-noarch-1 kdeedu-3.5.1-i486-1 kdepim-3.5.1-i486-1
kdeaccessibility-3.5.1-i486-1 kdegames-3.5.1-i486-1 kdesdk-3.5.1-i486-1
kdeaddons-3.5.1-i486-1 kdegraphics-3.5.1-i486-1 kdetoys-3.5.1-i486-1
kdeadmin-3.5.1-i486-1 kdelibs-3.5.1-i486-1 kdeutils-3.5.1-i486-1
kdeartwork-3.5.1-i486-1 kdelinks-1.3-noarch-1 kdevelop-3.3.1-i486-1
kdebase-3.5.1-i486-1 kdemultimedia-3.5.1-i486-1
kdebindings-3.5.1-i486-1 kdenetwork-3.5.1-i486-1
but I guess you can do without the games, toys and edu
the first one is the locale/language stuff, and if you use english, that is all you need, anyway, make your choice from slackware/slackware-current/slackware/kdei.
also make sure you have qt-3.3.5-i486-1.tgz (also in /kde)
go here to get package help/info:
http://www.slackware.com/config/packages.php