Bitcoin is a peer-to-peer electronic cash system that is completely decentralized, without the need for a central server or trusted parties. Users hold the crypto keys to their own money and transact directly with each other, with the help of a P2P network to check for double-spending.
The Open-Transactions project is a collaborative effort to develop a robust, commercial-grade, fully-featured, free-software toolkit implementing a full-strength financial cryptography library, API, CLI, and prototype server. Open-Transactions democratizes financial and monetary actions. You can use it for issuing currencies/stock, paying dividends, creating asset accounts, sending/receiving digital cash, writing/depositing cheques, cashier's cheques, creating basket currencies, trading on markets, scripting custom agreements, recurring payments, escrow, etc. Strong crypto is used. Balances are unchangeable (even by a malicious server). Receipts are destructible and redundant. The transactions are unforgeable. The cash is untraceable. The cheques are non-repudiable.
Moneychanger is a GUI built on top of Open Transactions, a financial crypto library. Moneychanger can be used to create pseudonyms, issue currencies, open accounts, withdraw and deposit cash (untraceable digital cash), write and deposit cheques, trade on markets, and much, much more.
finic helps users manage their finances. It can be used on a local network (as a client-server system for many users) or on local computer (client only for one user), with separation of accounts, clauses, and customers. It can encrypt information and manage different users with different access rights. Reports can be generated as HTML, PDF, or XLS files or through an internal print preview system. An API is available for creating extensions.
openHBCI is a C++ library for the German HomeBanking Computer Interface. It includes some tutorials for testing the library. Its current capabilities include complete key management on disc (RDH) and/or chip-card (DDV), the ability to perform single customer credit transfers, and the ability to get balance reports.
JHBCI is JCA/JCE cryptographic service provider for Java. It is useful for building HBCI home banking applications (clients and servers). JHBCI implements all relevant "RDH" crypto algorithms for the German Homebanking Standard HBCI Version 2.2, such as DES, RSA, ISO9796-1:1991-Signature, and RIPEMD160-MessageDigest.