Looking up the traditional Chinese characters of a word, many calligraphers will have different traditional Chinese characters. What's the name of that website?

First of all, the traditional Chinese characters in China are used in newspapers, magazines and books before 1953. So, you are only referring to the different glyphs written by ancient and modern calligraphers for thousands of years.

If you are interested in font research, you can look at The Chinese Dictionary, a sub-column of China Natural History. There are real Cao Li seal characters and different writing methods in it.