DIY dry erase boards are simple to make with a few things you have handy (or can pick up on your next thrift shop run).
Start with a picture frame that still has the glass in place. Put something monochromatic inside–a piece of scrapbook paper, fabric, an old grey t-shirt–that’s light enough so that your writing will show up against it.
Next, get a dry-erase pen and attach it with a string or a tiny Velcro dot. That is all there is to it! You’ve got a place to write messages to your roommates and reminders to yourself. This could be the easiest DIY project of all time!