Stealth X Ray Minecraft Mod
The Stealth X Ray mod allows you to see through 'walls' in Minecraft by removing blocks from your field of vision that don't interest you. Want to see through the ground and note where the diamond is? Use your powers of X Ray vision to hunt for diamond deposits, find caves and generally hack the heck out of your minecraft experience. This is a useful mod for people who insist on mining all their own materials instead of just using INVedit, but who want to make the process as streamlined as possible.
The X Ray mod can be toggled on and off by pressing 'x'. To select the ores you wish to lay eyes on, 'ctrl+x' is the key. This mod is therefore useful not only for looking for diamond, but for hunting rare Lapis Lazuli and other minerals of interest. Is it technically cheating? Sure, but Minecraft is a sandbox game, and you should be the one to determine how you play in your sandbox.
Multiplayer Applications
X Ray mods, wireframe texture packs and invisible player skins are all highly contentious topics in the multiplayer community at the current time. As a general rule you should be aware that this mod will probably be regarded as a 'hack' and it is possible that you will be kicked / banned from a server for having it installed, let alone using it. However this mod does not 'report' itself to the server like other similar mods do (hence the 'stealth' tag) so unless you behave in a highly objectionable way, people may never know you have it enabled.
The Stealth X Ray mod may even come in handy for server admins looking to keep an eye on activity occuring on their servers. As with most tools, the damage isn't done by the mod itself, but by how people use it.
Obviously this mod has a high capacity for griefing, but lets face it, if you grief a server worth playing on, you'll only ruin your own experience by getting your account banned. A good server is a rare thing, so if griefing your way out of good play experiences sounds like fun to you, there's probably something a little wrong with you on the inside and you should seek hugs immediately.
Installation
Installation is fairly simple, but requires Mod Loader. As most mods now use Mod Loader, this probably won't be too much of a hardship.
Direct Download Link (Included in case the Minecraft forum has one of their regular changes of hearts and decides that this is a griefing mod.)