Here are some plugins I consider important to be ported:
- Ban Manager. http://dev.bukkit.org/bukkit-plugins/ban-management/
- Multiverse (included all the extras as Portals, Inventories, etc*). http://dev.bukkit.org/bukkit-plugins/multiverse-core/
- MobArena. http://dev.bukkit.org/bukkit-plugins/mobarena/
- Quests. http://dev.bukkit.org/bukkit-plugins/quests/
- dynmap. http://dev.bukkit.org/bukkit-plugins/dynmap/
- War. http://dev.bukkit.org/bukkit-plugins/war/
- Coreprotect. http://dev.bukkit.org/bukkit-plugins/coreprotect/
- WorldBorder. http://dev.bukkit.org/bukkit-plugins/worldborder/