OnSpeed is a great tool which can be used for saving Bandwidth while working on the net . As well as incresing your browsing speeds it also decreses the BW usage by some sort of compressing the data before it gets downloaded .  It can be found here  .

If you got a Broadband connection and BandWidth is a primary concern for you , then this tool is for you . I cannot try it right now as in my college i get 24 hrs net without any limit of uploading/downloading . One of my friends has been using it with his Dataone Broadband and getting good results .