I've _finally _posted my instructions for getting ColdFusion 9 up and running on VirtualBox! It took me a few times to work through the process and get everything working (and documented) and at one point I forgot the password on the VM image and had to start over again. Oooops.
Documentation is now on my wiki: VirtualBox and ColdFusion 9
What will you end up with? A 'virtual' server running Apache/ColdFusion 9/MySQL. Using VirtualBox's shared directories you can access your code on the guest system. This seemed to be the most simple and flexible way to configure things. In my example I'm sharing the CFEclipse workspace directory but if you are using something different it should be easy to adjust to your configuration.
You could certainly run a GUI version of Ubuntu and install an IDE so you would have a self-contained development environment but with this example I wanted to create a system I could use at work and at home for various projects but not necessarily share the code and settings between them.
If you try this and run into any issues with the documentation - please contact me with corrections!