Calibre might be able to do it, but I'm not sure about that. But you can use the Send To Kindle app available from Amazon for free. Download it to your computer, drag and drop your books into it, and they go directly to the Cloud. You can also email books to the Cloud using the email address assigned to your Kindle or other device. This email address is in the MYK pages somewhere. They just redesigned them so I'm not sure where they put it.

ETA: Send To Kindle for PC and Send To Kindle for Mac.