What exactly are you looking for? Something that's mainly a good source for recommending new stuff to read, or something that's good for analyses/dissections of completed series you've presumably read?
Online reviewers often mix the two, and I don't really like going into a new series without having a chance to form my own opinion first. Some older blogs are better for the "post-mortem" kind of dissections, but they're hardly prolific, and I'd be surprised if any of them are even updated anymore.
Honestly I'd probably prefer a regular discussion/thread the most, when the people involved are putting in the effort and are less scared about coming off as pseudo-intellectuals.
Who are your favorite reviewers/bloggers?
Me. I'm the best reviewer. In this week's seminar we'll be discussing
Mikako-san, its central themes about the senseless lack of direction and coherence of everyday life, and whether the series and its characters actually deliver on this premise.