How can I convert .CR2 to .jpg? Is there a simple tool that will convert .cr2 files (Canon RAW) to .jpg? 

I know Preview does it well but I'm looking for something directly accessible from the contextual menu.
You can make a custom workflow to do this as a Finder (or even system wide) service using Automator.

Look for the Change Type of Images action under Photos and then you just need to decide on your workflow - whether you save this as a service that can be activated by the contextual menu or perhaps make it into a drop folder so you can automate the next step of the process as well.