Ahhh, where to begin?

How about http://www.usb.org/ ??

First, you can't "big-bang" USB. Read up on it and you'll realize why.

If you want to use USB in a project, you can buy micros from various vendors that implement the USB Serial Interface Engine in hardware. These micros aren't even all that much more money than micros without such support.

Depending on your application, you might not even have to write a host driver. Are you doing an audio project? All of the major OSes have Audio Class support. Does your device have to send only a few bytes to and from the device? Then you can use the HID (Human Interface Device) class, even if your gizmo isn't an HID.

-a