If you like the goodWeather gdesklet you should check out liquid weather
for KDE. It runs in superkaramba. Also, if using KDE for Slackware I recommend installing the Dolphin file manager. You can find it at slackbuilds.org/repository/12.0/system/dolphin/
Slackbuilds.org has a lot of nice scripts to install software for Slackware. If you cannot find a buildscript src2pkg would be the next best thing. You can update software that comes with slackware by using updates from current or even rebuild them with the official slackbuilds. You can easily keep up to date with security updates by joining the security mailing list. Slackware 12 is pretty current so you shouldn't have to update too many things to build the latest version of some program.
Welcome to Slackware