In Web 1.0, a small number of writers created Web pages for a large number of 
readers. As a result, people could get information by going directly to the 
source: Adobe.com for graphic design issues, Microsoft.com for Windows issues, 
and CNN.com for news. 
Enter Web 2.0, a vision of the Web in which information is broken up into 
“microcontent” units that can be distributed over dozens of domains. The Web of 
documents has morphed into a Web of data.
To summarize, these are what we see as the six main themes covering design in the Web 2.0 world:
1. Writing semantic markup (transition to XML) 
2. Providing Web services (moving away from place) 
3. Remixing content (about when and what, not who or why) 
4. Emergent navigation and relevance (users are in control) 
5. Adding metadata over time (communities building social information) 
6. Shift to programming (separation of structure and style) 
http://www.digital-web.com/articles/web_2_for_designers/

เว็บ 2.0 หมายถึงการเปลี่ยนสภาพของเว็บ จากแค่ผลรวมของเว็บไซต์หลายๆ แห่ง 
มาเป็นโครงสร้างพื้นฐานทางคอมพิวเตอร์ที่ให้บริการซอฟต์แวร์ผ่านเว็บให้กับผู้ใช้. 
ผู้ที่เห็นด้วยกับแนวคิดนี้คาดว่าบริการต่างๆ บนเว็บ 2.0 
จะมาแทนที่ซอฟต์แวร์แบบดั้งเดิมหลายๆ ประเภท
Web 2.0 is the business revolution in the computer industry caused by the move to 
the internet as platform, and an attempt to understand the rules for success on 
that new platform. Chief among those rules is this: Build applications that 
harness network effects to get better the more people use them. (This is what I've
elsewhere called 'harnessing collective intelligence.')
http://en.wikipedia.org/wiki/Web_2.0
http://www.oreillynet.com/pub/a/oreilly/tim/news/2005/09/30/what-is-web-20.html
http://www.seomoz.org/web2.0/ (***)
http://web20workgroup.com
http://www.web2con.com
http://www.wired.com/news/technology/0,1282,69114,00.html
http://blogs.zdnet.com/web2explorer/
http://www.programmableweb.com/apis
http://www.profitpapers.com/dev/web-20-design-tutorials.php

web 2.0 design
http://www.webdesignfromscratch.com/web-2.0-design-style-guide.cfm
http://www.digital-web.com/articles/web_2_for_designers/

web 3.0 = semantic web
http://evolvingtrends.wordpress.com/2006/06/26/wikipedia-30-the-end-of-google/
http://en.wikipedia.org/wiki/Semantic_Web (สมมาตร)
http://www.w3.org/2001/sw/

The concept of "Web 2.0" began with a conference brainstorming session between O'Reilly and MediaLive International. Dale Dougherty, web pioneer and O'Reilly VP, noted that far from having "crashed", the web was more important than ever, with exciting new applications and sites popping up with surprising regularity. What's more, the companies that had survived the collapse seemed to have some things in common. Could it be that the dot-com collapse marked some kind of turning point for the web, such that a call to action such as "Web 2.0" might make sense? We agreed that it did, and so the Web 2.0 Conference was born.

Web 1.0	-	Web 2.0
DoubleClick	-->	Google AdSense ?
Ofoto ?	-->	Flickr ?
Akamai ?	-->	BitTorrent
mp3.com	-->	Napster ?
Britannica Online ?	-->	Wikipedia
personal websites	-->	blogging
evite ?	-->	upcoming.org (Event DB) ?
domain name speculation ?	-->	search engine optimization
page views	-->	cost per click
screen scraping ?	-->	web services ?
publishing	-->	participation
content management systems (CMS)	-->	wikis
directories (taxonomy) ?	-->	tagging (folksonomy) ?
stickiness	-->	syndication ?

Many people use the term "Web 2.0" to describe:
+ http://www.webdesignfromscratch.com/web-2.0-design-style-guide.cfm