Always think before you post! Everyone (including you! - and I) make mistakes at times.
Download ANY Minecraft release here (.jar files)
How to use custom jars in the new launcher here
This tutorial has been out of date since early last year; you have to also edit the json file to remove the download URLs for the jar or the launcher will redownload it even if you renamed it:
(everything highlighted on the right side needs to be deleted so it looks like the left side, although you should leave the "assetIndex" section near the bottom in so the launcher knows what assets the game needs*. Note that you do not need to delete the downloads for any other files)
*Note that the new launcher fails to correctly download assets for 1.6.4 and older versions; you need to use the old launcher to download them, after which you can use the new launcher (I only found out about this after somebody installed one of my mods and had no sound, as I had the assets downloaded from playing on the old launcher before).
1/25/14: Updated again.
Always think before you post! Everyone (including you! - and I) make mistakes at times.

Download ANY Minecraft release here (.jar files)
How to use custom jars in the new launcher here
When I go to launch Minecraft, it re-downloads the .jar for the version that I'm using and it replaces my custom one. How do I stop that?
Holy Crap it works! Thanks!
I LOVE CATS!

This tutorial has been out of date since early last year; you have to also edit the json file to remove the download URLs for the jar or the launcher will redownload it even if you renamed it:
(everything highlighted on the right side needs to be deleted so it looks like the left side, although you should leave the "assetIndex" section near the bottom in so the launcher knows what assets the game needs*. Note that you do not need to delete the downloads for any other files)
*Note that the new launcher fails to correctly download assets for 1.6.4 and older versions; you need to use the old launcher to download them, after which you can use the new launcher (I only found out about this after somebody installed one of my mods and had no sound, as I had the assets downloaded from playing on the old launcher before).
MCL-4334 Minecraft gets reinstalled everytime you launch it
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?