I just warned my siblings who were considering using LocalBitcoins.com to buy at today's bargain-basement prices that the prices offered by the sellers (especially GBP) are totally off kilter. The reason being most traders use a calculation for their dynamic pricing that includes the mtgox price.
I'm finding the most reliable way of getting an idea of bitcoin valued in usd now is to use
BitPay's listed prices (or formula).*
So what I'm recommending my siblings do (and will offer you folks too) if intending to buy on LocalBitcoins whilst MtGox is broken is to click on whatever you need to to get a phone number then make contact with the seller to ask if they would set their price manually to reflect (plus whatever commission they normally would add) the BitPay price. You have the justification if you wanted to make a purchase from the many services offering BitPay as a payment option that is the calculation that would be used to calculate your bill in bitcoins.
So don't lose out
* I actually like the principle behind BitPay's means of calculating price and would like to see it more widely used. I have a variation on it that uses the top four USD exchanges by volume as listed on BitcoinCharts.org/markets that uses the average of the pair of Asks that are closest together.