Historical Market Depth - http://quant.stackexchange.com/questions/3078/historical-level-2-data-market-depth

whats the cheapest available historic data for fx and commodity futures? - http://www.linkedin.com/groupAnswers?viewQuestionAndAnswers=&discussionID=24166774&gid=155986&trk=EML_anet_qa_ttle-dnhOon0JumNFomgJt7dBpSBA

Get free tick data from US market - http://www.quantshare.com/sa-426-6-ways-to-download-free-intraday-and-tick-data-for-the-us-stock-market http://blog.quandl.com/blog/quandl-open-data/ http://www.quandl.com/WIKI https://blog.quandl.com/api-for-stock-data

http://quant.stackexchange.com/questions/141/what-data-sources-are-available-online

http://quant.stackexchange.com/questions/10838/bloomberg-ticks-is-difference-from-reuter-ticks

Sample of using quandl - http://www.automatedtrader.net/articles/strategies/156770/fetching-market-data-into-excel-using-python

http://blog.fosstrading.com/2017/06/yahoo-finance-alternatives.html