I have a dry-erase board in my room with the same notes I left for myself several months ago. I found that post-its work much better for what I was trying to do with it -- provide reminders for myself. The only thing to refine was a slight bit of resistance in finding a post-it, writing the reminder, and affixing it to the door, but I found a hack.

I had been thinking of getting one of those pop-up post-it dispensers (especially after seeing the Machinist), but I just couldn't justify the (albeit relatively low) cost, since it's really not that hard to put up a post-it as it is.

My hack, then, is to put a bunch of blank post-its in some pattern (I made them say 'Hi' this time) on whatever surface you normally use so they're already there when you want to use them.