What is Web 2.0
First off, these links might help explain it.
ZDNet Whiteboard Session on Web 2.0
The Infamous Wikipedia has something about it
O'Reilly is king with a diagram
If you didnt get it, then this is the Kabaweb explanation.
Kabaweb Web 2.0 : Some History and Evolution
An introducton on Web 2.0
The years following the "dot-bomb" crash resulted in the mundanity of the web. Pages became more like corporate badges, the Flash hype died, and checking email became another ritual. Then something beautiful happened. The web as we know it was Reloaded by the ingenuity of certain websites like Google Maps, Digg, Wordpress, Flickr, Youtube, and Facebook. People made sites that were dynamic (AJAX) in content and functionality. They also allowed the sharing of information between the individual and its community.
Now let us evaluate these technologies through its evolution.
CGI stands for Common Gateway Interface. It is merely program that can be run to grab dynamic content from your webserver based on what variables you pass through it. CGI most commonly was written with PERL since there was no need to compile. Even through this term is no longer use, the foundation of web applications use the concept of CGI.
Java Applets became popular for items like website Menus. The issue was that Java would have to be loaded on every machine and Java itself took long to load. The majority of consumer sites have stopped using this, however, internets and IT monitoring systems may still use them
Web in Transition
XML became an important movement since it offered structure and easily identifiable tagging to sections of a markup document. It was 10 times more powerful as HTML. There are even XML databases and certain data transfer takes place with an intially conversion to XML. It is still alive and kicking.
LAMP is the combination of Linux, Apache, Mysql, and PHP(or Python/Perl). Check out my AMP section for details and guides. Most people that want to have dynamic websites use LAMP. Even this site is on LAMP. This is because the technology is completely free.
Web Services including fancy things like SOAP and REST. They are really a cross-site query and response system. An example would be that a Website might make a request for all predicted weather in the US on April Fools Day. It would send a SOAP request and the weather database would only be providing that specific information. It is very handy and still is alive today.
Rails is a web framework for the Ruby language. It is one of the hottest technologies around. The theoretical concept that it seperates Model(database), View(page), and the Controller(actions,events) makes every piece of writing ruby modular. It is not strongly typed, enabling smaller and easily interpreted code.
Social Networking is really the idea that sites that embrace their community. Also, there is a notion of the Web being a Platform for everything. They do use technologies like AJAX.
Sample 2.0 Links
Web 2.0 Expo
Go2Web20 Web 2.0 Directory
Web 2.0 Validator
YouTube Web 2.0
Web 2.0 List
Web 2.0 Show
Use a Web 2.0 Browser