Ledger is a powerful, double-entry accounting system that is accessed from the UNIX command-line. This may put off some users - as there is no flashy UI - but for those who want unparalleled reporting access to their data, there really is no alternative. Ledger never creates or modifies your data. Your entries are kept in a text file that you maintain, and you can rest assured, no automated tool will ever change that data. Ledger is 100% currency-agnostic. You can store multiple currencies in any account, convert between them, or even pay in one currency and receive change in another. Ledger is international. Although UTF8 support is not quite there yet, Ledger uses ISO format dates, attaches no meaning to the naming of accounts, and can accept data in either US or European decimal formats. It will report currencies back to you following the manner of your own entries. Ledger uses a simple set of base commands which can be extended in countless ways. You can create monthly reports, average reports, check account balances, reconcile accounts, keep track of capital gains on stocks, etc.
WWW: http://www.ledger-cli.org/