Check out our feature package on Web 2.0, including an in-depth article on the technology infrastructure needed to create Web 2.0 applications.

This is my favorite part, though (because I was involved in creating it): An interactive timeline tracing the history of Web 2.0, from the creation, 10 years ago, of the BackRub search engine, which became Google, to the first blogs, to the 100 millionth MySpace page.

Tomorrow kicks off the Web 2.0 Conference in San Francisco, co-sponsored by O'Reilly Media and the parent company of this blog, CMP Media.

As a journalist, I get hives when people sling around marketing buzzwords, and "Web 2.0" is in danger of becoming a meaningless buzzword. But it seems to me that it has not reached that point, at least not yet. Web 2.0 is a useful phrase, describing a whole pack of design and business principles that go into the best Web sites and Web applications today.

The key characteristic, I think, is that Web 2.0 sites are built in collaboration with users. Flickr and YouTube are collections of photos and videos created, uploaded and managed by users. The content on those sites is owned by the users, and, in effect, loaned to the sites in exchange for the services those sites provide in managing the content.

Web 2.0 applications often have some other characteristics, most notably use of technologies such as RSS and Ajax. But those characteristics aren't essential to Web 2.0 the way user collaboration is.

What do you think? Is Web 2.0 a real trend, or just a marketing buzzword?