With a market capitalization of more than $8 billion, Bitcoin is by far the most important crypto-currency in the world.
At its current price of $621, the total supply of 13 million Bitcoins is worth more than 30 times as much as the total supply of the second largest crypto-currency, the Litecoin. CoinMarketMap tracks hundreds of virtual currencies, but none comes close to matching Bitcoins' relevancy.
Albeit still being a niche payment method, Bitcoin is slowly moving towards the mainstream as high-profile companies such as Dell have started to accept it as a legitimate payment option.
This chart shows the ten largest crypto-currencies, based on their market capitalization in July 2014.
You will find more statistics at Statista