I've recommended it before, but I continue to be amazed by the consistently high quality and erudition of the essays in the Claremont Review of Books. If I were to cut down my subscriptions to one journal, this would be it. 'nuff said.
UPDATE: I should point out that the Review is not a libertarian publication, but promotes its own idiosyncratic brand of natural-rights-based conservatism, which is apparent in some, but not all, of the essays it publishes. But I don't have to agree with every essay to appreciate the quality of the writing and editing.
Therefore, I am forced to read it from the web site. I guess I could subscribe, but I get so many publications now I just do not have the time nor the inclination to keep current. In fact, I sometimes feel overwhelmed.
I also find it curious that unlike other publications, Claremont Review of Books, does not publish the email addresses of any of its writers or staff. In fact, neither does its parent, the Claremont Institute.
I don't doubt that the Claremont Review also runs rigorous, carefully factually substantiated analyses of politics, philosophy, and current events. But at a glance, it appears to be the National Review upon stilts.
I used to subscribe but, like David, couldn't free the time necessary to read it. The best reviews are those that are not immediately politically charged.
It's kind of like Scalito. It's new and scary, and then it just kind of fades away when everyone realizes it's hyperbole.
Now, it's a ways from this to any manner of actual "conspiracy," but there is a direct intellectual lineage from this to the modern neoconservative tradition.