Is there any way to redirect a USB port on a local machine to and RDP connection with rdesktop to a Windows terminal server?

It depends on what you mean by 'redirect'. If you mean using the new features of RDP 6 (in Vista for example) for transparent use of devices like usb cameras, scanners, printers etc, then no, rdesktop (and afaik no other linux rdp client) cannot do what you want. I'd have thought that sometime in the future it'll become available, but since it's only recently been added to the RDP protocol, the rdesktop developers will take a while to catch up.

However, if you're just wanting to mount a usb stick, then you can forward that to a server, and it'll appear as a network drive. But I'd have thought 'hotplugging' the device will be problematic to say the least.

Thanks for that.

So how do people solve the problem of users wanting to transfer stuff from their USB sticks to their desktops?

Well the only way I know of is to do something like:
The command line above exports the directory /mnt/usb on the client which shows up on the remote desktop as a mapped network drive named 'usb'. If you have the usb automount on the client, and then export that directory, you should get close to what you want.

Good luck.