Last week when Office 2007 Beta 2 TR was released there was several people who were asking how they could retrieve their Product Key. Keyfinder Thing Lite can recover your Windows or Office keys and that includes Office 2007! Both the lite and the full versions are free and there is nothing to install, just download the file and run it.
The full version of Keyfinder available has a slightly nicer interface but it requires .NET 2.0 FX to be installed. I recommend just getting the small Lite version because it is simple and quick to use.