nari,
It depends on how you wan't to go about it. I know that the PIC18F4550 has USB integrated and that on windows it is treated as a serial port so the code is quite simple.
Otherwise maybe have a look at some of the ICs of FTDI that provide a USB-Serial conversion and thus you can use any MCU. I also know Atmel has a USB chip but am not familiar with Atmel ICs.
start with USB2.0 specs. As you plan to develop the microcontroller side hw/sw, that part is quite easy compared to the driver development on windows side. You can use Jungo to start with.