Generally the biggest bitcoin exchanges to buy cryptocurrency will be toward the top of the above list. For example Bitfinex, GDAX, Bitstamp, Coinbase (also the best usd bitcoin exchange) all represent large volume proportions. Daily volume varies, and therefore the world’s largest cryptocurrency exchange vary each day. Go to bitcoinity for a good list of all the best bitcoin exchange site to buy cryptocurrency and their proportional volumes. Some find this handy for arbitrage between markets.
There are also "stake grinding" attacks which require a trivial amount of currency. In a stake grinding attack, the attacker has a small amount of stake and goes through the history of the blockchain and finds places where their stake wins a block. In order to consecutively win, they modify the next block header until some stake they own wins once again. This attack requires a bit of computation, but definately isn't impractical.
Localbitcoins is quite a popular for p2p (person to person) transactions all over the world. Simply put, you interact directly with the guy selling to you. Out of all the bitcoin sites listed here, this is one of the first and most reputed. Escrow and dispute resolution is provided by the site. See my thorough review of Localbitcoins, I personally use it to cash out of positions quite often.
Bitcoincharts is the most popular website for following the current bitcoin price. The site provides a rundown of all major btc exchanges by volume. You can also arrange the markets to only display the Euro or the Japanese Yen versus bitcoin on the different exchanges. Like the name says, the website also offers charts with several popular technical indicators. The choice of timeframes ranges from 1 minute all the way to the Weekly TF. Plus, you get to see the current market depth at the different exchanges.
Altcoins are the new kid on the block and they are as unpredictable as they are exciting. With the biggest altcoins vying to take the top spot from bitcoin, they are all attempting to carve their own niches, with goals nothing short of re-imagining the way we do business, how we send and receive money, and how we transfer assets like properties and cars.
You'd have to get a fast mining rig or, more realistically, join a mining pool--a group of miners who combine their computing power and split the mined bitcoin. Mining pools are comparable to those Powerball clubs whose members buy lottery tickets en masse and agree to share any winnings. A disproportionately large number of blocks are mined by pools rather than by individual miners.
What’s so special about Bitcoin? There are many arguments on whether the new virtual currency will succeed or fail. We will not get into this nor discuss the politics behind the project. Our concern is strictly with the profit opportunities provided by this new payment phenomenon. In the next few pages on the new digital currency we will outline our thoughts from the perspective of a trader and a potential investor in this upcoming market.