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

• Zoom: click-drag
• Pan: shift-click-drag
• Restore zoom level: double-click

Price data begins on 2010-04-25 at $0.003/BTC, using the daily volume-weighted trading price of the first Bitcoin exchange, BitcoinMarket.com (PayPal USD trades). It actually started operating on 2010-03-17, however trading data for the first few weeks is—to my knowledge—not available. Data for 2010-07-18 and later is from the CoinDesk BPI.