Not sure about heavyweight coasters Diane, but i spent the afternoon alcohol inking plain white ceramic tiles with the kids, they look well funky.
I guess they could be used for coasters or trivets. Not sure how the ink would react to heat though come to think about it?
The cheap basic tiles go for about 20p each in most places like B&Q, i guess you could add stamps, embossing, paint effects and other stuff to it. Our local art shop sells them for 20p, i'm just off to get another 20 for us to play with.
Not sure about anything else though, not heavyweight anyway.