That said, we're sure to have left off a few (or perhaps even a few dozen) that deserve to be included. Feel free to add your suggestions in the Comments section below.
One quick note about operating systems: Many of these open source developer tools run on a wide range of OSes. In some cases, they support more than a hundred different platforms.
For the sake of keeping the list short and readable, we noted whether each developer tool supports the big three Windows, Linux and OS X. If you want to know whether a particular tool will run on Solaris or FreeBSD or another platform, you can click the link to check its Web site.
More than 1,000 groups use Bugzilla to track their software bugs, including Mozilla, Facebook, the Linux kernel and NASA. The Web-based system makes it easy to manage code changes, issue patches and stay in communication with other members of your development team. Operating System: Windows, Linux, OS X
The GNU bug tracking system stores information about software defects in a central searchable database. It can be accessed via a variety of interfaces and can send communication to team members as needed. Operating System: OS Independent
A competitor to commercial software like Blaze Advisor and JRules, Drools describes itself as a business logic integration platform for rules, workflow and event processing. It includes five separate modules: Drools Guvnor (BRMS/BPMS), Drools Expert (rule engine), Drools Flow (process/workflow), Drools Fusion (event processing/temporal reasoning) and Drools Planner (automated planning). Operating System: OS Independent
Javadoc uses the comments you embed in your Java code to create an HTML documentation file. By default it describes the public and protected classes, nested classes (but not anonymous inner classes), interfaces, constructors, methods and fields. It's included in Oracle's Java developer kits. Operating System: Windows, Linux, OS X
Like Javadoc, phpDocumentor turns code comments into readable documentation for users, only in this case for the PHP language instead of for Java. It's very fast and includes a variety of templates. Operating System: OS Independent
Intended as a replacement for Microsoft's .Net, DotGNU provides a variety of tools to compile and run applications. It currently supports C and C#. Operating System: Windows, Linux, OS X
The "GNU Compiler Collection" offers front ends and libraries for C, C++, Objective-C, Fortran, Java, and Ada. It's probably the most widely used compiler for code that will run on multiple operating systems. Operating System: OS Independent.
"Minimalist GNU for Windows" ports the GCC compilers and GNU Binutils for Windows. It allows you to use GNU tools to build Windows apps from Windows or Linux systems. Operating System: Windows, Linux
Formerly known as Pro64, Open64 was created by Intel and the Chinese Academy of Sciences. It includes compilers for C, C++ and Fortran90/95 compilers for the IA-64 Linux ABI and API standards. Operating System: Linux
Now owned by Oracle, the "worlds most popular open source database" counts Yahoo, Alcatel-Lucent, Google, Nokia, YouTube, and Zappos.com among its users. It's highly scalable, flexible, fast, and has become the "de facto standard for high-traffic Web sites." Operating System: Windows, Linux, OS X
MySQL may boast the "world's most popular" title, but PostgreSQL stakes its claim as the "world's most advanced open source database." Version 9.0 was just recently released and offers built-in binary replication, hot standby, easier permission management and several other new features. Operating System: Windows, Linux, OS X
Hadoop offers a variety of tools for working with large amounts of data in distributed computing environments. Notable users include Yahoo, Facebook, Google, Hulu, IBM, LinkedIN, The New York Times and others. Operating System: OS Independent
GNOME's IDE supports C and C++ development on Linux systems. It includes an application wizard, interactive debugger, source code editor, version control, GUI designer and more. Operating System: Linux
This cross-platform C++ IDE is highly extensible, making it easy to add the features you want. It includes built-in compiling and debugging capabilities, plus an easy-to-use interface. Operating System: Windows, Linux, OS X