Today is Ubuntu Release Day, so it’s a perfect time to learn how to use zsync in order to save some bandwidth. Of course, you can (and should) use it other days and for other purposes 
If you don’t know what zsync is, here’s an explanation: zsync is a file transfer program that allows you to download a file from a remote server, where you have a copy of an older version of the file on your computer already. This way, zsync downloads only the new parts of the file. It works using the same algorithm as rsync, but it can do the same over HTTP.
Updated
Here could be a nice video showing a demonstration of this tool, but it seems WordPress.com doesn’t show Blip.tv videos 
. So you have to go to LinuxJournal to see that cool thing.
(Spanish)
Para quien no entienda el vídeo anterior o prefiera las instrucciones en texto, aquí hay un post que explica lo mismo.
