I actually don't subscribe to any, but whenever I'm at a place that sells magazines, I usually check them out. My two favorites are Paste (I've actually met the editor of this one) and Q Magazine, which is British. http://www.pastemagazine.com/ http://www.q4music.com/
I really like Mojo, great value for money considering that they include a free CD every issue and that they don't review all same crap Top 40 stuff the American mags are. Ironically it seems that a disproportionate number of records/artists that they cover are Americans.
Mojo... Since I've started working here at MP3.com, I've become pretty fond of the website www.popmatters.com. They have an excellent combination of social commentary, music, film, books and pop culture in general. They even once had an article, just prior to the Champions League final, on how important Jamie Carragher is to Liverpool. I swear to god.