Okay so I was bored so I figured I would make a guide on how to install Mods on Mac OS X.
From what I have done it seems very simple to install and get the mod to work.
Step 1. Find the Mod in which you want to install in your game, I will be installing ReiMiniMap which I downloaded from http://minecraftdl.c...is-minimap-mod/ here. When you download it save it some where you can find it easily.
Step 2. You must find the minecraft folder in which your minecraft.jar file is stored within Mac OS. To do this I simply use Terminal and just do a direct command to open the folder. If you do not have Terminal on your Dock then you can go to spotlight in the top right hand corner of your screen and search for it. Once you have terminal open you can copy and paste this command into it to open your minecraft folder. open ~/Library/Application\ Support/minecraft
Step 3. Once you are in your minecraft folder you need to find the bin folder which is shown in this screenshot. -> http://i45.tinypic.com/ta3jmp.png Open the bin folder and locate your minecraft.jar file. Use a program like Zipeg to extract the files into a folder. This is where you will add the mod files so you can load them onto Minecraft.
Step 4. Loading the mods into your minecraft.jar folder that you just extracted which is no longer a .jar file it should be a folder. It should look something like this. http://i46.tinypic.com/2s180t3.png Once you have this folder opened and all the files extracted you can open the folder where you have your mod stored and copy the mod into the Minecraft folder. Once this is done you are able you can change the filename of the folder from Minecraft to minecraft.jar this will make the Minecraft launcher read this file as if it was the normal minecraft.jar file. After this is done find the META-INF folder and delete it.
Step 5. The folder will look like this after you have added the .jar extention to the end of the folder. http://i45.tinypic.com/x3inu1.png once this is all done you can put the newly made minecraft.jar folder back into your bin folder (if it's not already there) and load up the game. If all went well the game will load up and you will have your mod installed on Minecraft.
This is how I install mods onto my copy of Minecraft on Mac OS X. If I have missed anything or if you would like to add to this just post it and I will add it to the thread to help our fellow Mac users. If you are having any trouble installing a mod on Mac OS X post it here and I will do my best to help you with your trouble.