* github: direct access to the remote github directory (issues, pull requests, etc.)
There's also a ton of language specific packages (lint, color scheme, etc.)
My main productivity tip would be to use the "ctrl + p" search command a lot. It matches searches very nicely (partial matching). One can look for files in the project, specific line in the active file (if you start with ":"), specific methods (if you start the search with "@"). ST3 also has a symbol lookup command which is really powerful ("ctrl + shift +r").