Woo a Minecraft server!
I will be sure to join this later if anyone else is on.
I have a few Mod suggestions.
Having never been on, I'm not sure if you have these or not...A list of the Mods you do have would be good on the main post :)
Anyway,
Over my time of playing Bukkit servers, I've found a few mods I really liked.
One is the Factions mod, this allows players to create a faction, they can have their friends join it and can build their own cities. The brilliant thing about this mod is that it allows the players to claim land under the faction, which allows for player controlled anti-grief. The main aim of this mod is to have enemy factions and ally factions and you all fight against each other, but I love this mod purely for the fact that it stops griefers in their tracks.
Another one would be, I think it's called the Lumberjack mod. Whatever the name is, I can't remember right now, this mod basically means that when you hit the bottom block of a tree, it chops the whole tree down. And I think as well, it might be this same mod, it might not...But when you chop a tree down, it plants a sapling in its place, making tree farms even more efficient.
One final mod that I also love, is something along the lines of Controlled Explosions. I can't remember the name, but it's a mod that stops creepers from damaging the environment around them. They still explode, and they still do damage to the players, but your area wont suffer for you accidentally running in to hug a Creeper. This also aids to stop griefers from just letting a creeper explode near them while near your house.
Now with all of this being said, I'm not actually saying that we have any griefers, these are more just a precaution and the fact that I love these Bukkit mods :P