Plugins to encourage "word of mouth" advertising.

[Brash]

Hey guys,
Does anyone have any good plugins that would encourage "word of mouth" advertising. I have gangs at the moment and it is working pretty well, but I still need more plugins that encourage this.
Thanks,
-Frats

 

[Speed]

https://www.mc-market.org/resources/181/ Wizard has a referrals plugin you could use

 

[Brash]

http://www.spigotmc.org/resources/meteorloot.7496/

Not sure how this encourages word of mouth.