Cypress has a dev "kit" for about $100 from digikey that enables you to create/build a USB <-> Serial convertor of your own. It has limitations on throughput and the driver is functional, but not included with on an out-of-the-box PC, so you have to use the supplied driver in the kit. Also, I use the term "kit" loosely because it's only software/firmware that you get. You have to make the hardware yourself.

Having played with it myself, it's kind of interesting but the FTDI one is probably more complete. The Cypress chip is about $1 in quantity though (just their standard low speed peripheral USB chip).

Now having said that, I find it distressing that Philips never included USB in their 8051's. They produced a peripheral (the 'D11) that was controlled over I2C. I made one product with that. The D11 is EOL now, I think. Plus it was goofy. But if Motorola can make HC08's with USB, there is no excuse that we can't buy an LPC9xx with USB. I have used the Cypress low-speed stuff (tools are horrid), and once you get over the 3 month learning curve, you can be quite productive.

GB