Links

Standards, specifications

List of all Java APIs (JSR's)
Entry to W3C web standards
RCF Editor (Official Internet Protocol Standards)

Development

NetBeans
Maven
JavaDB, Derby
QUnit
Git Tutorial

HTML

HTML vs XHTML vs Polyglot HTML
HTML5 Compliant tutorial
HTML5 Compliant tag reference
HTML5 (CSS,JS) Presentation from Google
HTML5 Flowchart (what to use when...)

CSS

CSS 3 tutorial/references (further down)

JavaScript

JavaScript (core) reference
JQuery API
QUnit (JavaScript testing)
HTML Landscape Overview (JS API's)
ECMA (JavaScript) specification
JavaScript Design Patterns
JavaScript API Demos (HTML5)
JavaScript in Detail, "this"
Gotchas

Java EE General

Different types of managed beans
CDI reference (Weld)
Bean Validation reference

WebServices/REST

Metro (JAXB implementation)
JAXB annotations
Jersey (JAX-RS implementation) User Guide
Article: Designing REST (HATEOAS)

Java Server Faces

JSF Home (Mojarra)
Nice overview article, JSF, CDI, ...
JSF tag reference
ICEFaces
ICEFaces ACE components
PrimeFaces
Full version CRUD demo (also database), JSF PrimeFaces.

Java Persistence API

JPA Reference
JPA JPQL Reference
JPA CriteriaAPI reference

Real Time Web

Long-polling, Comet, etc. explained
Why asynchronous processing is the new foundation of Web 2.0
ICEFaces push (PushRender API)
Asynchronous Servlets
Server Sent Events Specification
Atmosphere (Comet, Web sockets, Server sent events,...)