I don't think I've really put a calendar to good use since my uncle sent me a Roald Dahl one when I was around 9, complete with sticker set (which I still have) and Quentin Blake illustrations. However, with my social life slowly becoming more hectic, all sorts of school related events, and a memory that still doesn't retain best friends' birthdays, I thought it was time to start using one again.
This calendar is a) free (for me, at least, it will cost a bit more if you don't have everything to hand, mainly the frame) b) reusable, c) incredibly easy to make, it took me less than half an hour and d) completely customizable, which is four big bonuses in my book.