The Power and Politics of Blogs by Daniel W. Drezner & Henry Farrell

here's an interesting read that comes close to my topic - from july 2004 by two assistant professors of political science at the university of chicago and the george washington university, respectively:

ABSTRACT
Weblogs occupy an increasingly important place in American politics. Their influence presents a puzzle: given the disparity in resources and organization vis-à-vis other actors, how can a collection of decentralized, nonprofit, contrarian, and discordant websites exercise any influence over political and policy outputs? This paper answers that question by focusing on two important aspects of the “blogosphere”: the distribution of readers across the array of blogs, and the interactions between significant blogs and traditional media outlets. Under specific circumstances – when key weblogs focus on a new or neglected issue – blogs can socially construct an agenda or interpretive frame that acts as a focal point for mainstream media, shaping and constraining the larger political debate.

even if they look at politics & blogs at a slightly different angle, their cited sources are very useful for me.
(in case you hadn't noticed: the headline of this post is linked to their paper as a pdf)