Where can I find historical exchange rate data for BTC/USD? I'm looking for historical exchange rate data for Bitcoins/USD beginning in 2010, but I haven't been successful. This is for academic research. I tried bitchart.org. I don't know how to access the MtGox API either. 

Can you help me with a step-by-step procedure to download the data in CSV format (or any other format)? It would be awesome if you could just provide me with the actual data file.
http://www.coindesk.com/price
http://www.investing.com/currencies/btc-usd-historical-data
http://www.quandl.com/c/markets/bitcoin-data
https://bitcoinchain.com/markets


Also, there was a Bitcoin Time Series spreadsheet.  Scroll to the bottom to see the data sources.