From SoftPerfect Research:
SoftPerfect Connection Emulator (SCE) software is aimed for network application developers, system administrators and network engineers. It is a WAN emulator that imitates a network connection with a low bandwidth limit, delays, losses and other problems. Using SCE you can test how well your application performs on a slow or long distance connection to ensure the quality of the product being developed. SCE runs on any PC with Windows 2000 or higher, allowing you to selectively apply bandwidth limits and simulates packet traversal issues to mimic a low-grade communication channel.