With the last major update (1.6.x I believe) where they re-wrote alot of the game the bin folder is no longer used. If you were to re-install minecraft it would no longer be made. There is actually a separate resourcepacks folder for texturepacks and a Mods folder.
If you use one of the mod loaders, like MCPatcher for example, it will automatically load your mods for you. I don't know if you HAVE to have a mod loader to use it but it helps.
You can put your texturepacks directly in the dedicated resoucepack folder now.
Go to one of the Minecraft WiKi's to read up on it as you can not mess with the other folders without buggering up the game.
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The minecraft.jar folder ( in the bin folder, in the .minecraft folder, in the application data folder) note, you will need to use an extracting program like winzip to open the folder
Mods can usually be downloaded from where they are publishedSome mods come with an installer to install the modFor other mods, you need to install them manually by opening the zip file they are in and copying the contents to the minecraft.jar file found in the bin folder of the .minecraft directory
Delete the bin folder in the .minecraft folder, start Minecraft, and it will say that it's updating. Let it update, then install all of the mods over again, but don't install the one(s) that you don't want.
Go to the %appdata% folder on your computer, then go to .minecraft, then delete the .bin folder.
I can answer this for Windows and Mac: Windows: Find your Minecraft folder (search: %appdata%\minecraft) and delete the folder named "bin". Re-open Minecraft and it will re-download the bin, fixing it. Mac: In Finder, go to your Hard drive (the silver rectangle that is named "HardDrive", users, your user name, library, Application Support, Minecraft, and delete your "bin" folder. Re-open your client and it will re-download the bin, fixing it.