For sharing code snippets you can just do something like this:

alias paste='curl -s -F '\''sprunge=<-'\'' http://sprunge.us | tee >(xclip -selection clipboard)'

Which on my system will create a paste of whatever you pipe to it and put the link to it in your clipboard.

How exactly would you imagine this being integrated with Slack? Would you want to share stuff from your terminal into Slack? Or you want to share content from Slack?