Here is the definition of Web2 from the above link:

"The phrase Web 2.0 refers to a perceived second generation of web-based communities and hosted services — such as social-networking sites, wikis and folksonomies — which aim to facilitate collaboration and sharing between users."

"The concept of Web-as-participation-platform captures many of these characteristics. Bart Decrem, a founder and former CEO of Flock, calls Web 2.0 the "participatory Web"[13] and regards the Web-as-information-source as Web 1.0."

Web 2 "Technologies"

• Blog
• Wiki
• RSS - Really Simple Syndication
• Mashup
• Social Networking
• Podcast
• content-management systems (CMS) like Joomla
• Folksonomies
• Rich Internet applications Java for example
• CSS Cascading Style Sheets "It is designed primarily to enable the separation of document content (written in HTML or a similar markup language) from document presentation (written in CSS)."

Useful Links

Top 25 Web 2.0 Apps to Help You LEARN

Learning 2.0 This is a program developed to train/learn some web 2.0 technologies, do 23 things and learnbydoing things like blogging, wiki, podcasts, etc.

[1] I found this link through a newsletter called "UK Fundraising News" ---- From the chat archive: AndriusKulikauskas:02:09 <AndriusKulikauskas> Web 2.0 is about a series of trends that are perhaps related [02:09] <AndriusKulikauskas> one is social - that people are participating by writing, not just reading [02:10] <AndriusKulikauskas> another is technology - AJAX - which means that you don't have to click a new page, but things can happen on the page that you are at, thanks to JavaScript and XML [02:10] <AndriusKulikauskas> but a lot of web 2.0 is "walled gardens" where they want you to be inside their space as much as possible and not be visible [02:11] <AndriusKulikauskas> so that part is not good for us and also the part about AJAX is not so good because that can be a difficult, closed technology