Read the 10.2 (stable) changelog. Patches/security updates are kept on the Slackware ftp site at:
ftp://ftp.slackware.com/pub/slackwar...tches/packages
You can pick through the ones you want to download, save them to a directory and run upgradepkg *.tgz in that directory to update the lot.
Alternatively, grab all the .tgz's - running upgradepkg *.tgz will only upgrade packages that are actually installed.
Running anything from -current is not guaranteed to work, and you may upgrade to a package from -current only to find it has different dependencies from the "stable" package. If you've messed it up a few times, you're probably better off sticking with stock 10.2 stuff (although firefox/thunderbird 1.5 are nice).