1) First and most important is to build your knowledge and information-gathering from the official sites that reflect their namesakes. For php information php.net is the best site. For jQuery the best is jquery.com. At these sites you can find the most comprehensive and accurate information about of these methods, functions, classes, and much more. You will also find, a lot of interesting questions and solutions on the forums. It is very important to be aware of all the updated and latest versions. Therefore, I recommend using the official documentation foremost, and then any resources at will.
2) Git hub A very popular resource of repositories, where there are the majority of source code plug-ins, frameworks and libraries. Here you will find information, tips and get steps, shortcuts and much more. With this resource, you can also set your own acquisition to the public.
3)Stackoverflow.com This resource is probably known to everyone who has ever searched something about web design. It contains a huge database of questions and answers. Stackoverflow.com is a very good and qualitative resource with the necessary information. The answers are often given by very skilled people.
4) net.tutsplus.com is a great resource of various types of video, audio, text tutorial. Authors often work in a reputable company, so the quality of lessons is very high.
5) jsfiddle.net. A very popular resource for testing JS, CSS, HTML. You can save your examples and share the link with others. It is often used for tutorials.
6) fontsquirrel.com this is a great resource for generating font-face fonts. It is an indispensable resource for front-end developers. Also google-fonts have become very popular.
8) prefixr.com This great resource is for anyone who bothers to put prefixes in their css code. It is very simple to use, just copy the code and resources will give re-generated code with prefixes.
9) caniuse.com This is an informative resource which contains information about certain technologies supporting browsers. It is always updated and the information is very useful for web developers who follow the trends.
10) css3generator.com This is a great generator for the majority of CSS3 styles. it offers a very easy and simple generator for those who do not remember the syntax.