Some time ago , I promised to put my Web 2.0 musings for science gateways on this blog. These actually turned into a tutorial and a short book chapter, linked below.
Web 2.0 Tutorial slides are here: http://grids.ucs.indiana.edu/ptliupages/presentations/Web20Tutorial_CTS.ppt
My related survey document is here:
If I was in charge, Web 2.0 would be called Web 2.0 Beta.
Finally, anyone who thinks the Semantic Web is "Web 3.0" should think again.