As it turns out there are several resources one can use for all main cryptocurrencies so I will post here the most relevant and flexible I was able to gather.
This page has data for: Bitcoin, Litecoin, Ethereum, NEM, Decred, ZCash (transparent transactions only), Dash, Dogecoin, Ethereum Classic, PIVX, Monero.
ETH - BTC
Poloniex As chart
Poloniex As JSON
One needs to edit the timestamps in the API to get a different snapshot.
And edit the period to adjust the details.
Coindesk Closing price and OHLC
Closing price blockchain.info
Bitcoin data on Quandl
Bitcoin data on Quandl II
Thanks to the answer to this question on Ethereum's stackexchange
I will keep updating this answer with more links as I find them.