SOS is pretty good, but pricey.
i've been subscribing to Recording Magazine for about 4 years now, and at first it seemed useful, but i've learned far more at this site than ever in the mag. the past 5 or 6 issues have been absolute wastes of time, and i'd say there are only about a dozen articles in the entire 4 years that i'd actually go back and reference now.
i'm definitely gonna check out tapeop--not familiar with it, but liking the high marks here.