I see that this thread was started a while ago. Blogs have probably progressed a bit since the early comments here. I find the ones that interest me most are written by musicians or people who focus almost exclusively on reviews.
A few I like:
1. Free Jazz
2. Point of Departure
3. Destination Out
4. Do the Math
5. Spider Monkey Stories
Some offer opportunities to add your comments, some don't. None that I've come across offer the wide-ranging discussions that take place at sites like Organissimo. They seem very specific in focus, which is where their strength lies, IMO.
Political or current events blogs are a different story altogether, with rambling discussions (shouting matches, flames, trolls, etc.) that go on forever. Extracting any insight at all from these discussions is pretty labor-intensive.
Anyways, my 2 cents.