I went on a survival server and apparently moderators can go into "Mod" mode where they can fly, walk through walls/noclip, have their name turn green, and cannot be killed by other players. Is a mod like this available for bukkit?
It's a client mod called zombe's mod pack (mycraft works too). To not get killed by other players use WorldGuard or Essentials and type /god. For walking through walls use WorldEdit's /thru. Permissions can change your name color.
You can also use my godPowers plugin for godmode, and it also has a few other fun commands you can play around with.