Often I need to explain people what the difference is between web1.0 design and web2.0 design.
There are some standards in web2.0. Take the header of this log as example; a small gradient and a reflection shadow.

There isn’t a specific book or what so ever about web2.0, but the big web2.0 sites share the following design features;

* Simple layout
* Centered orientation
* Design the content, not the page 3D effects, used sparingly
* Soft, neutral background colours
* Strong colour, used sparingly
* Cute icons, used sparingly
* Plenty of whitespace
* Nice big text

A proper article about the web2.0 design can be found right here.

Layout and the specific use of images isn’t the only thing that makes a site design web2.0. The colors also matter.
In my search for a webpage with the web2.0 colors a I saw a few weeks earlier, I found a lot of other sites with web2.0 color schemes, except for the one I was looking for… Well, this overview is also fine;

(click to open site in new window)

This is also a nice overview with examples from which site they’re taken.

I also found this nice and handy tutorial how to make a web2.0 logo in Photoshop.

Update:

Found the web2.0 color scheme site I was looking for; Daily Color Scheme . com!
There are some good examples of color schemes from populair websites!