Soon, CTRL-S is going to be a thing of the past. Mac OS X Lion brings us Autosave and Versions, two features that are going to save you a lot of trouble when editing documents.
With Autosave, Apple automatically saves your documents when changes are made. But instead of overwriting the previous save, changes are filed into different document "Versions," which you can browse and restore.
Right now, Autosave and Versions only work in a few Apple-branded apps like iWork and TextEdit, but expect to see integration into third-party apps soon.
Get started with these new, headache-saving features with this How To: