DwarfCraft is a RPG-like plugin for minecraft (via Bukkit) that allows players to improve their characters.
Players(Dwarfs!) may pay materials in a school area to improve a skill level, which will provide benefits
such as increased weapon damage, decreased tool durability drop, increased drops from blocks or mobs, etc.
  
Data used for this plugin comes from two places: 
On each load, a list of skills and effects is pulled from flatfiles.
Dwarf's skill levels and world training zones are kept in a database (currently supports only sqlite)  

Useful commands to get started: '/dc help' '/dc tutorial' '/dc info'