Boost Build / Bjam syntax highlighting for Sublime Text. Not great, but better than nothing.
Find the directory where Sublime puts all of its packages and stuff. In many versions of Sublime, you can just click on "Preferences" followed by "Browse Packages" and it will open the directory up for you.
Open up a terminal (or command prompt) and cd into this directory and clone this project:
git clone https://github.com/TimSimpson/Sublime-Bjam.git
Now back in Sublime Text, open a Boost Build file. Click on "View", then "Syntax" and click on the "bjam" option which will have just appeared.