Do you keep a bunch of dried out Sharpies wasting space in your pen holder? DIY blog The Art of Doing Stuff suggests you can often revive a permanent marker by soaking it in rubbing alcohol.
All you need to do is pour a little rubbing alcohol into a cap, soak the marker until you see ink swirling out, and then put the marker’s cap back on for 15 minutes while it dries. Once the time is up, you should have a marker working like it’s brand new. If you’re working with non-permanent markers, you can get the same results by substituting water for rubbing alcohol.