http://www.dallaway.com/sloppy/
Sloppy is a very useful tool for testing websites over 56K modems.
It simulates slow connections (configurable from 9.6K to 512K) and runs as a proxy so you can see how fast your site will appear on, say, a dial-up.
Simple idea worked with great effect, and a must for web developers who all-too-often work comfortably on high-speed connections without realising how painful their glorious designs are to load on dialup.
Best of all, it’s a Java Web Start application – runs right from the website, and in various operating systems.