Minecraft 1.2.5 (Size: 51.47 MB)
Minecraft Alpha 1.2.5
The list of changes can be found on notch's blog: http://notch.tumblr.com
Donations can be given at http://nekio.com
The update files go in .minecraft\bin
There is a windows installer for those who don't already have minecraft. You can use it just to update too.
If you want to get the files in it to do a manual install, use 7-zip or winrar to extract them and put them in "username\appdataoaming\.minecraft". If you have xp its "username\application data\.minecraft".
I don't have linux or osx so I don't really know where the files go if you are using a linux os or a mac.