10
Trading on Mt. Gox, which is now the largest Bitcoin exchange, started in July 2010 at an exchange rate of $0.05 USD. This comment suggests that on May 2010, bitcoins were traded at bitcoinmarket.com for roughly $0.004 USD.
What other exchanges existed this early in Bitcoin's life? What is the earliest/lowest recorded exchange rate?
4
According to https://en.bitcoin.it/wiki/History:
2009 October 5 Exchange rates published by New Liberty Standard. $1 = 1,309.03 BTC (and theymos thought NLS was overcharging[3])
It cites http://newlibertystandard.wetpaint.com/page/2009+Exchange+Rate and https://en.bitcoin.it/wiki/History#cite_note-2
That first citation seems to have a decent list of pre-May 2010 exchange rates.
2That's cool. I still think there's room for more detail in the scope of this question (e.g., how much volume did NLS have with these rates, other early exchanges and their starting rates). – Meni Rosenfeld – 2012-11-20T18:06:55.443
1Yes, maybe someone who was actually around (in 'the Bitcoin world') back then could shed some light on the volume of NLS. Also, I would expect the most volume at the time to have come from OTC trades, so maybe someone can chime in with their anecdotal experience for that time frame. – smickles – 2012-11-20T21:23:36.877