Alright, we're getting a new plugin called BlockOwn, which can be found at this link:
http://dev.bukkit.org/bukkit-plugins/blockown/.
Basically, what this plugin does is make ANY block you place owned by you and only you. Other people can access your blocks ONLY IF you allow them to, meaning that griefing any blocks you place is nigh impossible UNLESS you give them permission to grief you, which in that case, there would be a different problem.
This plugin will log every block you place from the installation on, so be aware, it will not yet protect structures you have already built. My suggestion is to find a way to limit access to pre-existing structures with new blocks, such as a protected wall or fence, and private all of your doors using /cprivate so that, if someone attempts to enter any structure you've built, they cannot break through a wall or enter through the door you've made.
Use /protect to protect EVERY BLOCK you've placed of the material you're looking at, or use /protect <material> to protect every block of the material you type.