sourceforge provides free & fast open source software downloads and development, and business software reviews and comparisons featuring the largest open source and business software directory.

stack overflow is the largest, most trusted online community for developers to learn, share​ ​their programming ​knowledge, and build their careers.

osdn is a free-of-charge service for open source software developers. we offer git/svn/mercurial/bazaar/cvs repositories, mailing list, bug trafficking system, bulletin boards and forums, web site hosting, release file download service, eternal file archive, complete backup and shell environment.

winmerge is an open source differencing and merging tool for windows. winmerge can compare both folders and files, presenting differences in a visual text format that is easy to understand and handle.

oschina.net 是目前领先的中文开源技术社区。我们传播开源的理念，推广开源项目，为 it 开发者提供了一个发现、使用、并交流开源技术的平台

github is where over 100 million developers shape the future of software, together. contribute to the open source community, manage your git repositories, review code like a pro, track bugs and features, power your ci/cd and devops workflows, and secure code before you commit it.

菜鸟教程(www.runoob.com)提供了编程的基础技术教程, 介绍了html、css、javascript、python，java，ruby，c，php , mysql等各种编程语言的基础知识。 同时本站中也提供了大量的在线实例，通过实例，您可以更好的学习编程。..

掘金是面向全球中文开发者的技术内容分享与交流平台。我们通过技术文章、沸点、课程、直播等产品和服务，打造一个激发开发者创作灵感，激励开发者沉淀分享，陪伴开发者成长的综合类技术社区。