Finance
* Adempiere — ERP Business Suite
* Buddi — for personal use
* OpenERP — ERP system
* Compiere — ERP solution automates accounting, supply chain, inventory and sales orders
* ComUnion ERP — web-based ERP system
* ERP5 — Python and Zope based ERP
* GnuCash — Double-entry book-keeping
* Grisbi — Single-entry
* HomeBank — for personal use
* jFin
* JGnash — Java-based, double-entry book-keeping
* JQuantLib — Java-based Quantitative Finance API framework for financial instrument valuation and more...
* KMyMoney — Double-entry book-keeping
* Marketcetera — trading platform
* Mifos — Microfinance Institution management software
* n21 eBusiness Suite — web based ERP / CRM
* OpenXpert/Xpert — Fund accounting on Linux and Windows 98/XP
* phpOrganisation
* Quasar Accounting
* QuickFIX/J — FIX protocol engine written in Java
* SQL Ledger — Double-entry book-keeping
* TurboCASH — Double-entry book-keeping for Windows
See also: Comparison of accounting software
Integrated Library System
* Evergreen
* Koha
* NewGenLib
* PMB
Mathematics
Main article: :Category:Free mathematics software
Modeling and Simulation
* PDQ (Pretty Damn Quick); a queue-theoretic analytic modeling package in C, Java, Python, Perl. and PHP
* SimPy; queue-theoretic event-based simulator written in Python
* blender; 3d modeling software written in python and c++
Science
Main article: :Category:Free science software
Geographic Information Systems
Main article: :Category:Free GIS software
Plotting
Main article: :Category:Free plotting software
Scanning probe microscopy
* Gwyddion — Scientific data analysis
* Gxsm — Gnome X Scanning Microscopy - dsp supported scanning probe acquisition
Microscope image processing
* CellProfiler
* ImageJ
* Endrov
Molecule viewer
* Jmol
* Molekel
* PyMOL
* QuteMol
Bioinformatics
* Bioclipse
* BioRails
* UGENE
* TreeSAAP
Cheminformatics
* Chemistry Development Kit
* JOELib
* OpenBabel