I have printed calendars but I tend to change things all the time so I decided that a dry erase calendar would be easier. I didn't want to spend the money on one though and I wanted it to be large enough to do two months at a time so I made my own using an extra dry erase board that we already had.
I use mine to schedule out blog posts so that I stay motivated and make sure that there is a variety of posts on the blog. It often changes based on which projects work out and which are flops, and what supplies I have on hand but it helps to be able to glance at it and have ideas for what to make when I have some free time. I also have colored x's under each title so I know right away which ones still need to be made, which have been made but need a post written, and which has been written and is ready in the queue.
You could use it as a family calendar or menu planner though. :)
I just used a yard stick and a black Sharpie to make the grid. Each box is 3"x3" but yours may vary based on the size of your white board. If needed you can clean the board with a wet paper towel but the dry erase board cleaner will make the Sharpie smear really bad. There might be other permanent markers that work better though.