The website linked in the title also includes a daily act of civility if you want something new every day.
So... first up a personal pet peeve of mine:
If you are invited to an event that requests an RSVP, respond, and do it in the time required. If you RSVP yes to an event, plan to show up.
Or let the organizer know as soon as possible if your plans change. Your RSVP could trigger decisions that cost money and time. Remember, too, that there may be someone on the waiting list who would be happy to take your place.