Is there a decent application for personal finances that support multiple currencies on OSX?
iBank sure does:


  Go global. Just like your Mac, iBank works worldwide. With multi-currency support, you can set a default currency for any account, download exchange rates and calculate transfers between accounts automatically. iBank supports localization for British English, and now includes full French language support as well.


MoneyWell does as well:


  Transaction-Level Exchange Rates
  Do you bank in multiple currencies? MoneyWell has you covered. You can track your spending in your primary currency while having accounts in several other currencies and store both amounts in each transaction.