Opera for developers
Opera cared deeply about web standards: its people helped write CSS, HTML5 and many other specifications, its engineers built Opera Dragonfly, and its developer network taught a generation of web designers.
Opera Dragonfly
Opera's built-in developer tools, introduced in 2008: DOM and CSS inspectors, a JavaScript debugger, a network monitor and remote debugging of Opera on phones and TVs.
Tools for other devices
Opera also published emulators so that developers could test their sites without the device: the Opera Mobile Emulator and the Opera TV Emulator.
Dev.Opera
Opera's developer network: tutorials on HTML5, CSS3, SVG, mobile web design, accessibility, extensions and widgets, and the Web Standards Curriculum written with the community.
Opera Labs
Experimental builds and technology previews: video on the Web, WebGL, device access, file I/O for widgets, Opera Mobile labs for MeeGo and Android.
Desktop Team blog
Week after week, the Desktop Team published snapshots, betas and release candidates on My Opera, and talked with thousands of testers in the comments.