Subscribe to Guitar Player (although sometimes I question why), Acoustic Guitar (which I think I'm letting lapse - wow, great start, eh?), Premiere Guitar and Vintage Guitar. Pick up the British mags - Guitarist, Total Guitar, Guitar Techniques - fairly often. Will pick up the very odd Guitar World now and then, but it's very rare anymore. Outside of the guitar mags, I'll pick up any of a lot of other instrument mags depending on what or who is in them - Bass Player, Keyboard, Rhythm, Modern Drummer, Drumhead, Drum, probably some others. Also grab Sound On Sound, Recording and Electronic Musician now and again. Also recently found a mag from Mac Video Pro - only runs $5 and has some pretty good recording tips in it. They've had deals in a couple issues (only four so far - it's a quarterly) for discounts on some plug-ins and things that have made it pay off well. And the occasional general music mag - Mojo, Classic Rock, Prog, Hammer, Revolver, etc.
I have a few subscriptions outside of music stuff and some general interest things I grab now and again. I just need more time to read - I've fallen way behind on stuff, and some mags get pushed to the side out of necessity (but I'm finding out what happened in Vintage Guitar in 20091).