Network tools that simulate slow network connection

try Traffic Shaper XP you can easily limit speed of IE or other browser with this App and its also freeware

On Linux, see netem: the kernel already contains support for traffic shaping, and can simulate high latency, low bandwidth, packet losses, and all sort of other adverse conditions, even on a loopback device (so you don't need a real, physical network to test across).

I am resurrecting this thread because I had the same need recently. Amazingly, I discovered that Fiddler can be used to do that by customizing the rules and adding this line oSession["response-trickle-delay"] = "150"; in the section OnBeforeResponse.

Fiddler is really amazing.