Grisbi - Accounting for everyone !
Zoho Invoice - 100% free online invoicing software for small businesses.
Ledger-cli.org - Ledger is a powerful, double-entry accounting system that is accessed from the UNIX command-line.
Kamerge - Kamerge simplifies & systemizes the key processes of your business.
Gnuaccounting - Gnuaccounting is a Free Java cross-platform accounting and bookkeeping application. Features
TurboCASH - TurboCASH Accounting Free and Open Source Accounting Software for Small to Medium Business.