Cliquet is a toolkit to ease the implementation of HTTP microservices, such as data-driven REST APIs.

Fast, JavaScript DSP library that creates JIT optimized audio callbacks using code generation techniques.
It is designed to be a fast audio API for browser based audio content.

A specification for building APIs in JSON. Clients built around JSON API are able to take advantage of its features around efficiently caching responses, sometimes eliminating network requests entirely.

This guide describes a set of HTTP+JSON API design practices, originally extracted from work on the Heroku Platform API.

API design guidelines from Paypal

Given a web API, Generate client libraries in node, php, python, ruby

localForage is a handy library that improves the offline experience of your web app by using asynchronous storage (via IndexedDB or WebSQL where available) but with a simple, localStorage-like API.

Collage.js brings together many public APIs, along a method of presenting media within a limitless two-dimesional space to create memorable experiences.

Turn websites into structured APIs from your browser in seconds

DevDocs combines multiple API documentations in a fast, organized, and searchable interface.

Put the internet to work for you.

History.js gracefully supports the HTML5 History/State APIs (pushState, replaceState, onPopState) in all browsers. Including continued support for data, titles, replaceState. Supports jQuery, MooTools and Prototype. For HTML5 browsers this means that you can modify the URL directly, without needing to use hashes anymore.

OpenKeyval is a completely open key-value data store, exposed as a drop-dead simple web service. The goal is to make this a very easy way to persist data in web applications.

A javascript library to hide differences between mapping APIs.

Anything To Triples (any23) is a library, a web service and a command line tool that extracts structured data in RDF format from a variety of Web documents.

YOURLS stands for Your Own URL Shortener. It is a small set of PHP scripts that will allow you to run your own URL shortening service (a la TinyURL or bitly).

A community-curated database of well-known people, places, and things

Pipes is a powerful composition tool to aggregate, manipulate, and mashup content from around the web.

Inspired by Yahoo's Pipes, DERI Pipes is an engine and graphical environment for general Web Data transformations and Mashup.

Calais is a rapidly growing toolkit of capabilities that allow you to readily incorporate state-of-the-art semantic functionality within your blog, content management system, website or application.