ConTeXt support is now integrated with AUCTeX. I'm maintaining and supporting this part of AUCTeX. I suggest you start using AUCTeX instead of downloading and using the package below.
In case you do not want to install AUCTEX, you can still use my ConTeXt Emacs mode: context.el. This mode extends tex-mode.el with ConTeXt specific features. See the context.README file for installation instructions and Emacs tips.