The N8 uses micro-a for usb on-the-go, which won't fit in a micro-b socket. But the only significant difference* between micro-a and micro-b is the shape and you can file a micro-a connector down so it fits in a micro-b socket.

* There is a pin on the micro-a/b connectors which tell devices which support usb-on-the-go which type of connection it is, but it is not used by the N900 AFAIK, so that difference can be ignored.