Most of the [examples](https://github.com/mbostock/d3/wiki/Gallery) provided are by the author, but there's also a great community writing plugins and more examples.
Ranked in these QuestionsQuestion Ranking
Pro Huge number of examples online
Most of the examples provided are by the author, but there's also a great community writing plugins and more examples.
Pro Large community
D3.js is a very popular tool with an active community, resulting in plenty of learning resources and fast responses to questions.
Pro Doesn't require a proprietary framework
D3's emphasis on web standards gives you the full capabilities of modern browsers without tying yourself to a proprietary framework.
Pro Versatile library for manipulating data on the DOM
Pro Very flexible join paradigm
Can be tricky at first, but once learned, data manipulation and binding can easily generate complex visualizations for massive amounts of data.
Pro Great for highly interactive scenes
D3.js offers incredible levels of interactivity.
Pro Backwards compatible
D3.js is intended for modern browsers, so supports IE9 and above (IE8 with an additional library) as well as all the other modern browsers.
Pro Feature rich
Effects: Anaglyph, cross-eyed and parallax barrier.
Scenes: add and remove objects at run-time; fog
Cameras: perspective and orthographic; controllers: trackball, FPS, path and more
Animation: armatures, forward kinematics, inverse kinematics, morph and keyframe
Lights: ambient, direction, point and spot lights; shadows: cast and receive
Materials: Lambert, Phong, Standard, smooth shading, textures, PBR and more
Shaders: access to full OpenGL Shading Language (GLSL) capabilities: lens flare, depth pass and extensive post-processing library
Objects: meshes, particles, sprites, lines, ribbons, bones and more - all with Level of detail
Geometry: plane, cube, sphere, torus, 3D text and more; modifiers: lathe, extrude and tube
Data loaders: binary, image, JSON and scene
Utilities: full set of time and 3D math functions including frustum, matrix, quaternion, UVs and more
Export and import: utilities to create Three.js-compatible JSON files from within: Blender, openCTM, FBX, Max, and OBJ
Support: API documentation, public forum
Examples: Over 150 files of coding examples plus fonts, models, textures, sounds and other support files
Pro Fallback canvas rendering
Three.js offers a canvas renderer as a fallback when WebGL is not available.
Pro Helpful and friendly community
Thanks to the recently introduced forum, it is easy to find a community of helpful developers.
Pro Actively developed
Three.js has great project health, with activity on Github daily for bug fixes and new features.
Pro Hundreds of officially maintained plugins, extensions, control systems, importers, exporters and special effects
The core of the three.js system is kept to a minimum to reduce file size, however there are also hundreds of extensions maintained in the offical repo on github, along with many free textures, fonts and models. You can find them all here.
Pro Support for special effects and postprocessing
Three.js support many special effects and post-processing filters including particles, lensflare, sprites, real time reflection and refraction and even area based lighting.
Pro Support for physically based rendering
With the introduction of the new MeshStandardMaterial, three.js support physically based rendering (PBR) out of the box allowing for real life quality material and lighting.
Pro Support for most industry standard file formats
Three.js has importers for most of the industry standard files format (obj, mtl, fbx, 3ds, gltf, collada, babylon, playcanvas, stl, vrml, draco and many more), making it easy to author assets in your favourite modelling software and import them for use them in three.js.
Con Steep learning curve
The complexity and flexibility of D3.js results in it being a time-consuming tool to learn for many users.
Con "Selections" are elegant, but somewhat hard to grok
Selections are core to working with D3 beyond the basics. They're powerful and useful, but require new developers to get up to speed (e.g. set aside 30m to read and digest: https://github.com/mbostock/d3/wiki/Selections) and if used in the context of a larger application will result in a portion of the code using different patterns than the rest, requiring a translation layer in between.
Con Lack of versioning system means that the API changes frequently
Three.js releases a new revision about once a month, and the API can change at any time. This means that a lot of third party help found online is out of date.
Con Weak visual tools
Three.js has its own editor but it has been weakly developed. It does not support a lot of engine features.