are there any sites that let you invest on the stock market using bitcoins?
You are asking if there are any brokers who accept funds in the form of bitcoins that would allow you to purchase stocks on the public markets?
There are none in the U.S. that (yet) provide that.
There are online brokerages in the U.S. that take ACH / direct deposit transfers, which would allow bitcoins to be traded for USDs and then withdrawn as an ACH. Any Bitcoin exchange that does Dwolla cash-out would work for this:
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http://www.MtGox.com -
http://CampBX.com -
http://FastCash4Bitcoins.comThere is one type of market where bitcoins can be used to speculate on gold, oil / crude (WTI), and dollars:
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http://ICBIT.seThere is also a bitcoin-based market where a handful of "equities" for unincorporated entities are traded -- MPEX:
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http://polimedia.us/bitcoin/mpex.phpThere are a couple of methods where bitcoins can be used to fund Forex trading accounts:
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http://www.bit4x.com/ -
http://www.LiteForex.comThere is a hedge fund that announced plans to invest in bitcoins as one of its asset classes:
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http://www.hedgeweek.com/2012/10/08/174393/emergence-electronic-gold%E2%80%A6There has been interest in something like what you are describing, but none to-date have progressed to where this is available today:
Real Life Stock Passthroughs (eg AAPL) -
http://bitcointalk.org/index.php?topic=112363.0Buy/Sell AAPL with BTC/LTC -
http://bitcointalk.org/index.php?topic=100688.0There isn't necessarily a good reason that this isn't available yet today -- as long as the broker performs the same AML/KYC as a broker that accepts fiat does. Because bitcoins can be used to transfer funds faster than a bank wire transfer even, it wouldn't be surprising to see support for Bitcoin as a funding method be one of the more common requests. It's a natural fit, so it will likely be happening. It is likely just a matter of time.