Well, the key is to order all of your magazines online so that they cost next to nothing.
New Yorker: Have for years, love the urban feel and the mix of arts & politics and 10,000+ word articles on very strange things. Most importantly, great writing and a great fact checking department.
The Economist: To the point, global, compact, and great writing and reporting. Plus the student rate isn't that expensive. It combines well with my Washington Post and WSJ daily subs.
City Journal: It's Quarterly, but is sort of like a more conservative free market New Yorker. Great articles with a different slant.
Atlantic Monthly: I read a lot of the articles online, and read a lot of Andrew Sullivan, so decided to support the magazine and pick it up in print as well (got 2 years for under $10 online)
GQ: For the pictures and ads, although British GQ is better it's just too expensive in the states. Personal interest in style/fashion/design.
Forbes: I let expire after they wrote an article titled "Love Global Warming" (http://www.forbes.com/forbes/2006/1225/038.html) written by the head of what is more or less an ExxonMobile thinktank. It was just too much for me.
Wired: Because it was free
Used to subscribe to Maximum PC (great magazine) when I use to tinker with computers more.
Magazines I'm looking at subscribing to:
HBS: For upcoming mgmt consulting job
Urban Land Institute: Due to a growing interest in commercial development, architecture, and urban planing
Probably a magazine on design/architecture... haven't decided what yet.