This is the most comprehensive all-time Bitcoin price history chart you will find online. Updated daily. The chart is interactive:

Price data begins on 2009-10-05 at $0.000764/BTC which is the earliest exchange rate published by New Liberty Standard, the first Bitcoin exchange ($1.00 buys 1309.03 BTC.) The historical exchange rate for early 2010 is available at this other archived page. The last known New Liberty Standard exchange rate is $0.005472/BTC on 2010-03-02.

The market price of Bitcoin is established again on 2010-04-25 at $0.003/BTC, using the daily volume-weighted trading price of the second Bitcoin exchange, (PayPal USD trades). The owner, dwdollar, actually started operating it on 2010-03-17, however trading data for the first few weeks is—to my knowledge—not available.

The Bitcoin exchange rate for 2010-07-18 and later is from the CoinDesk BPI.

All this comes originally from Thank you, Marc!