TortoiseSVN for Windows

If you'd like to use Subversion on Windows, you might want to use the TortoiseSVN client. It lets you use commands and see the status of files from within Windows Explorer.
Operating System: Windows

Learn More...

Valgrind

An open-source debugging and profiling tool suite

Valgrind is an instrumentation framework for building dynamic analysis tools. Valgrind tools can automatically detect many memory management and threading bugs, profile your programs in detail, and to build new tools. The main 6 production-quality tools are: a memory error detector, two thread error detectors, a cache and branch-prediction profiler, a call-graph generating cache and branch-prediction profiler, and a heap profiler.

ArgoUML

Open Source UML Modeling Tool

The self-proclaimed "leading open source UML modeling tool" supports diagram editing for all 9 UML 1.4 diagrams and comes in 10 different languages. Because it's based on Java, it runs on any platform, and it can export diagrams in 6 different file formats - GIF, PNG, PS, EPS, PGML and SVG. Another nice feature is that it supports reverse engineering with Jar/class file importing.

PhoneGap

Open source Mobile Framework

PhoneGap is a free and open source framework that allows you to create mobile apps using standardized web APIs for the platforms you care about. It enables software programmers to build applications for mobile devices using JavaScript, HTML5 and CSS3, instead of device-specific languages such as Objective-C.