JQuery PHP library
Very frequently you’ll write AJAX code with a server-side language, often PHP. This library adds a jquery object to PHP. You can use jQuery-style syntax within PHP, and the library automatically writes the jQuery code and sends it to your browser.
W3Schools tutorials and examples
W3Schools has become a go-to site for tutorials. There are a lot of tutorials about a lot of topics. The quality varies, but most are quite good. Note that some of the tutorials are out of date. Standards have changed over the years, and it’s hard to tell which tutorials are following standards from several years ago, and which are using the current best practices. Still, this is a site worth bookmarking, and if you can’t find what you’re looking for in this topic, you might find it there.
Google AJAX APIs
Google has been extremely committed to the AJAX and open-source movement. The company has released a number of incredible APIs that allow developers access to powerful Google tools. Investigate how to connect to Google Maps, Google searching, visualization tools, and even Google Earth!
A powerful alternative to jQuery, Dojo has a very strong user interface library. Dojo widgets (dijits) are the Dojo answer to user-interface objects. The many very powerful dijits in Dojo include tools for date and time input, data tables (which automatically retrieve data from an AJAX request and then populate an HTML table), and menu systems.
As Yahoo has built cutting-edge AJAX applications, it has also released its own development library for programmers. The Yahoo User Interface (YUI) is an incredibly powerful application tool with DOM support, event management, and a huge number of components.
My favorite feature of this very nice developers’ news site is its reference cards. The site has a huge library of quick-reference cards on just about any development topic you might consider. Each card is available as a free, downloadable PDF. (I actually wrote the XHTML reference card.)