There are at least a dozen "major" exchanges around the world that do significant volume in a given space of trade pairs. Poloniex is an excellent option for a first time exchange account as they vet their available trade pairs well, and only make available what has a significant enough volume developed from other exchanges to support their customers' divestiture should they decide there exists some good reason to liquidate (i.e. truly worthless claims, dodgy mods, fraud, technical problems, etc). Some of the other exchanges like Bittrex or CCEDK use the power of being able to offer listing to a small coin for a larger cut of the transaction fees, and provide a means of capitalization through trading into bitcoin and the others available. As soon as you can trade a coin newly minted into an exchange of any sort, make no mistake that "money" is being "created" just like a central bank does, except the new "money" is in our decentralized open-source ledger rather than the fed's centralized closed-source private/public banking cartel. Additional major players in the exchange game are obviously those of eastern origin, such as BTCe and BTC38, both Chinese. The last group of players would be the futures markets that offer some simple options trades or highly leveraged margin accounts like Bitfinex and BitMex. To give you an idea of the ability they now wield, Bitfinex was being criticized in April for being "insolvent," but have sinced launched IOTA which peaked at a market cap of nearly $1.8B. Value that they created. In their computer. The current market cap is at a paultry $800M, but you can bet they can pay their bills now. For a long time.
Sorry for the red pill. I do that sometimes. Most times. =]
Start with Polo. Follow the rabbit hole down from there. =]
G3
Another chinese site which has english is Yunbi. But you need a chinese bank acct.
I wanted to get PAY & MCO so I signed into BITTREX. They have lots of alt coins there