Brian Dorey has been working on a USB communications box project:
Several of the projects we have been working on recently needed some form of serial communication with our PC, either through RS232, UART, I2C or SPI and at the moment we use a handful of different USB to serial adapters designed for each different protocol. One problem we have run into before is ground loops between the PC and the devices under test can occasionally cause problems. What we needed was a single communications box that works with all of the normal communications protocols and is isolated from the PC. After looking at some of the isolated USB to RS232 converters that are on the market we decided that we would build our own.
Project info at Brian Dorey’s blog.