I don't know of any free softwares for it, but the instructions are available from both, so it shouldn't cost you anything to format your data the way they specify and just upload it. Are you having any trouble with the instructions they are providing? If so please explain in detail.
Do you already have a file with your raw product data? If so, it's just a matter of manipulating the data to match the format Froogle is asking for. If you read the page from the link I posted there, it's really straight-forward with only key fields needed.