I really like coindesk, I think it is overlooked by many. But give it a look at:
http://www.coindesk.com/price/With it you can pick between like 5 or so different exchanges, or their own BPI. But I think it is big as you can select the exchange you use as all exchanges will vary on price some ... so most accurate is kinda hard to say I think unless you specify exchange. Also I love it goes down to 1 hour you can watch current trends or go out much larger on timeframe. So give it a try.
I would agree bitwisdom is also great they are king in my eye's as far as ROI calculator. They have one of the best and most comprehensive there is there. And it's pretty good on using to guess next bitcoin difficulty change with current data.