Slackware repos?
 

Does Slackware have some sort of repository were I could install programs from there instead of looking for sources online?

Slackbuilds.org, Slacky.eu and LinuxPackages are probably the best known, there are others.

I personally prefer Slackbuilds.org as you get the slackbuild and source and compile it yourself. Their selection is limited at the moment compared to the other two. Slacky.eu usually provides a slackbuild, LinuxPackages only sometimes. Some packages from Slacky.eu and Linuxpackages can have unnecessary dependencies.

Also crucial: http://www.slackware.com/~alien/slackbuilds/

http://wiki.linuxquestions.org/wiki/Slackware-Links has all that you need and more ....