Well, there has always been pkgtool which has a dialog-based interface but I guess that's not what you want.
This release now has slackpkg which will automate some package-related tasks. Speaking of which, I'm going to grab my external hard-drive, check I have the latest rsync and slacpkg upgrade-all (that's not the only thing to do in general but I've already done the first part).
And there is also sbopkg which you can get at sbopkg.org and which uses slackbuilds.org to build packages. Also, if you're on slackware64, export ARCH=x86_64 before running sbopkg.
Slackpkg is highly-regarded (enough to make it into slackware ;) ) and sbopkg is too. You can use them without worrying.