An interesting analysis of top  100 blogs (18 February 2008)
http://technobabble2dot0.wordpress.com/2008/02/18/top-100-analyst-blogs-2/

You will find
- list of 100 blogs
- methodology of ranking (determined by PageRank, subscribers, recent inbound links, frequency and focus of posts as well as the number of comments)

 I sometimes try to use ask systems.
One of the questions to www.ask500people.com is about

What are the best tools for creative expression in Web (Web 2.0)

It might be interesting answers:
- blogs - ------------------  32 %
- social networks - ----  29
- discussion forums -   26
- mashup-----------------  13.

You can ask other question as well.