What Can I Use on my Crown That Fell off Yesterday to Tide Me over Until Monday when my Dentist's Office is Open?

You can try to keep the area clean and do nothing until you see the dentist as soon as possible. You can also try a temporary cement that you can find at the pharmacy or even grocery store. There are two that come to mind...one is Denttemp crown cement and the other is Polygrip.

If you can get it back into place-practice a few times- then using a denture adhesive such as Poligrip could suffice for the short term.