Well, the title says it all.
I have no problem with resolving dependencies on my own, but when I uninstall a programm, how could I keep track of the dependencies, thus remove them?

Is there a possibility to store this information in the /var/log/packages files, or better yet, is it possible to include the dependencies in the the .tgz's, so a 'removepkg' would get rid of them as well?

No, you have to track them down on your own as well.

In Debian the program is called deborphan, this is not possible with Slackware because there is no dependency database. SalixOS which is compatible with Slackware lists all of the dependencies for both their own and Slackware packages.

Packaging the dependencies with the package is not a good idea, as a dependency may be required for multiple packages, and if you removed one of these mega bundles you would break several others, there is also the risk of dependency hell where different versions of an essential program are required by different programs. They try to replace each other and therefor at least one program can never work, or worse your entire system dies.

samac

There was and probably still is (see slacky.eu) a utilitiy called slackdeptrack that displays all dependencies of all ELF executables and libraries by walking through your filesystem so it is, or at least was, possible to figure out packages no other package depends on. It was several years ago I played with this tool so I cann't guarantee or even recommend it because I don't know its current state. I simply did not need such feature ever.

slackdeptracj still works fine. But, it shows you the packages needed by each package -not the 'reverse' depends( list of all packages which depend on a package)

Are we referring to packages that come with Slackware or others that were installed (and maybe also built) by the sysadmin.

For the former, I would ask Pat :-), for the latter it is up to the sysadmin to keep record.