Soulver supports 164 real world currencies, updated hourly from CurrencyLayer.com.
To perform a currency conversion, use the currency's 3 letter code, and convert using
10 USD in EUR | 8.88 EUR20 GBP as AUD | 36.29 AUD1500 RUB to DKK | 152.65 DKK
The entire list of supported currency codes can be found at CurrencyLayer. It also includes some commodities, like gold and silver spot prices.
You can perform a historical currency conversion which uses the rates on a particular date in the past:
10 USD in EUR on March 20 | €8.371 BTC in USD one year ago | $10,230.82
Soulver supports live rates for 16 popular cryptocurrencies. Rates are updated hourly from Nomics.