I remember someone at one of the shows talking about using a LINIX box for a delay simulator...I don't remember the details other than it used two NICS and twiddled with some of the Kernel settings.
There is a product called "The Cloud" that lets you take snapshots through a LAN/WAM, then emulate the environment (latency, burst patterns, etc) for testing purposes. It's PC-based, I believe it Windows of some sort.
FWIW
Scott