A very easy way to make USB communications to your microcontroller is to use the UART of the microcontroller and attach that to a chip like the Silicon Labs (Cygnal) CP2101. Access info here....

http://www.silabs.com/products/...erface.asp

In the microcontroller software is very easy,,,just like UART. On PC side it is as easy as using COM port as well. This solution comes with a very simple driver that requires no work on your part. The USB connection can virtualize the serial connection up to very high effective baud rates.

Other types of smart microcontrollers with on-board USB controllers or using off-board chip require much more work on the PC side in terms of getting an application to talk to the remote microcontroller. Some vendors offer some generic device drivers for the USB port which give you a head start while on the other end of the spectrum there are appproaches where you will be buying USB device driver books at Amazon.com and you will be wondering why you ever started this project.

Michael Karas