These are a few of many plugins you should consider before you release your server to the world.
The plugins listed below can prevent griefing and alert you of anything dangerous in the world.
Other plugins below are for admin to use to just keep and eye on new people joining your server.

Firstly you will need WORLD EDIT, world edit can change, add and remove any block anywhere in your minecraft world. You can claim locations that only the people you set can make any changes to the selected region. This is great against griefers as it protects anything inside that barrier. Including, chests, walls, floors, roofs, levers, doors. Anything inside the region cannot be touched unless authorized by the region owner.
You can download Worldedit here: dev.bukkit.org/media/files/537/760/WorldEdit.jar

Another vital Plugin you will need is WORLD GUARD, World Guard allows you to set doors, chests, levers etc to private. So only you and the admin and open or use this object.
READ: All you need to do is have a sign, place it on a chest and it will be claimed as yours, the writing will already be entered onto the sign once you place it. It should read: [Private] and the your username underneath it. For a door you will need to enter that above it. [Private]Under>[Username] you can download World Guard at: www.minecraftforum.net/topic/79679-pluginbukkit-worldguard-50-protect-your-world-14/
For other commands and information on world guard read the forum attached to that link.

Another Useful Plugin for admin is SIMPLE ADMIN, I personally find it useful for clearing other peoples inventory if I don't agree in what the user has in their inventory. There are other uses for simple admin that you can find out about in the forums.
You can download Simple Admin here: dl.dropbox.com/u/17402100/SimpleAdmin.jar

Another plugin for your new server would be MOB DISGUISE, Mob Disguise can change you into any type of mob whether it be a pig, cow, sheep, chicken, squid, giant, creeper, spider, zombie, skeleton and so on. Its a simple command just type /md [mob] and you change into that mob. To change back its just a simple /md.
You can download Mob Disguise here: raw.github.com/desmin88/MobDisguise/master/MobDisguise.jar

Yet another Plugin for security purposes is BIGBROTHER, Big Brother monitors a selected users every move, you could be out mining, or building and this person could be stealing, collecting lava, or even damaging a block of sand, choose what to get notified about and what user.
You can download Big Brother here: ci.nexisonline.net:8080/job/BigBrother/Recommended/artifact/target/BigBrother.jar

Every wanted to know if your community have secret chests or rooms in another location, because WINSTONS XRAY TEXTURE PACK turns almost everything to glass, you can read more about it in the forums. You can use it for finding underground mines, spawners, ores and chests. You can even watch other people from the other side of the map. This is a useful plugin and is recommended for server owners. You can download the texture pack from here: www.onehitgamer.com/attachments/winstons-x-ray-pack-2-5-zip.461/

Another useful plugin for all admin and owners, INVISABILITY: Is used to follow and keep an eye on people you don't know, don't trust or maybe even just want to muck around with them. Other Admin can see you but regular people cant. You can download this plugin here: dl.dropbox.com/u/16258042/SpyerInstaller.jar

For More Plugins Visit my Other Topics or search up the forums.

-Pan