Is anyone aware of a website that tells you the various formats of public keys/private keys of the main crypto currencies?
I'm not aware of such a website.
But what I can think of is you can try to use BIP39 tools(
https://iancoleman.io/bip39/). I'm not sure that is what you actually need, but as a surface, it will give you public/private keys on various cryptocurrencies, since most major altcoins are already supported by HD wallets.
Upon opening that website, just click "GENERATE" to create a random mnemonic. Then, on the "Coin" form, select the cryptocurrency you want. After that, you should be able to see the chosen cryptocurrency public/private keys in the "Derived Addresses" section.