I am building a small robot running the Linux 2.4 kernel (XBow Stargate single board computer). It has a USB port, which I hope to use to read in analog sensor data and control several relays on the robot.
I am seeking a USB device to facilitate this operation. Is anyone familiar with such a device? I have had no luck so far searching for one, but its operation seems to be something that would be frequently needed for projects.

My plan is to interface with this device in C++.

The computer can be found at xbow.com/Products/productsdetails.aspx?sid=85 for those interested.

There are USB data acquisition development boards like:
http://www.ftdichip.com/Products/EvaluationKits/DAQ.htm

One that simulates an RS-232 interface would be the easiest like the following.
http://www.circuitcellar.com/library...e177/index.htm

An interesting website.
http://www.activewireinc.com/