Saves me lots of frustration when switching between projects.
You can download and read more about what it does here: https://bitbucket.org/fuglesang/sublimetext-project-sessions/
This plugin listens to the opening and closing of projects in Sublime and stores your sessions on a per-project basis. And when you open up the project again it re-opens the files you had open when you closed it.
Hope people who wants this feature find it as useful as I do.