As far as I know, unfortunately, there is none. I don't know if there is an apps that might help you, but in the Droid itself, you are stuck with the hard keys. Truthfully, I, myself, prefer the hard keys. Had a phone with soft (icon) keys which I was continuously, accidentally, touching and messing me up.
Re: Is it possible to change hard navigation buttons to icons on droid x
There is not a setting on the phone that will allow you to change the hard buttons. You can search the market place to see if there is an app that will allow you to do so. Keep in mind that the apps are third party apps and they are not supported by Verizon Wireless.