I purchased the HomeTrends Tablecloth Protector from Walmart for $5.00. The one I have is clear vinyl, oblong and 60 inches wide by 108 inches long. It does a great job of protecting your tablecloth from spills and stains, while letting the beauty of the tablecloth show through.
I have also used this same type of protector as a mattress protector. Years ago, before my father passed away, he was bedridden and had an indwelling Foley catheter. He very often would have leaks and accidents in bed, and laying this vinyl protector over the mattress and then putting the bed linen on top of it saved the mattress from being ruined. If you have relatives who are bedridden and have accidents in bed, or children who wet the bed, this is a great way to protect the mattress. Plus, the vinyl is comfortable to lie on. It can be easily wiped clean with a damp cloth or sponge.
The HomeTrends Tablecloth Protector is a nice buy and can be used for more than just protecting your tablecloth. The vinyl will rip over time, but it is inexpensive enough that it doesn't really present a problem for me to just go out and buy another one when needed.