Netcraft, reports that last month saw the largest increase of sites ever since it began the surveys. The reason for the jump? They say partially it was due to blogging sites:

The Internet experienced its strongest site growth ever last month, powered by a surge in blogs and free web sites. In the June 2006 survey we received responses from 85,541,228 sites, a gain of 3.96 million sites from the May report. This is the largest one-month increase in sites in the history of the Netcraft survey, surpassing a gain of 3.3 million in March 2003, although the 2003 gain was larger in percentage terms (8.5%, compared to 4.7% this month).

You can read more about it in their June 2006 Web Server Survey.