Sublime Text edits since last save

Add this line to your Preferences.sublime-settings file (If you're on a Mac, then open the Sublime Text 2 menu -> Preferences -> Settings - User):

"highlight_modified_tabs": true

This will highlight tabs that have unsaved changes.

You can install the FileDiffs plugin which among other useful things will give you a diff between the current (edited) file and what is saved to disk.

You may use the "Marking Changed Rows" plugin, which places a small gutter marker for lines with unsaved changes.

I know this already has an accepted answer, but it is not necessary to install FileDiffs or anything else. Just right click on the modified window and select Show Unsaved Changes.

A pane will show up at the bottom, listing the differences. There isn't an obvious way to dismiss the pane, but Ctrl+F will replace it with the search pane again.