I get Smithsonian and Scientific American. My family aren’t big readers, so I subscribed to these myself in my teens, only to catch everyone reading them at one time or another. At my place, they’re still lying around but people get distracted by the motor mags (Octane, Classic Bike).
I was going to say “People”, but then I remembered that I have one of those electronic fly swatters that does the same job, but better.
And now for something completely different…Eating Well magazine is $10 a year, and my 8 year old is responsible for creating a menu one day a week from it. It’s one less meal I have to plan, it’s all pretty healthy stuff, and I haven’t had a dud recipe yet. She loves to page through it and plan, and she’s learning a lot about cooking terms reading the recipes. She’s beginning to do quite a bit of the cooking too, although I still do the dangerous parts. The next step will be for her to create a meal with a *budget *(she’s partial to the shrimp and steak recipes. 
)
As most of the suggestions are for “grown-up” magazines (although of course kids like them too), I’d also suggest a couple of kid oriented magazines to get them into the habit of magazine reading. Ranger Rick ($15/year) and Cricket($33.95/year) are classics which are still full of great content.
Sicks Ate already agreed, but I have to second this/these. 
I love Popular Science. The only other magazine I get is MIT Technology Review: that subscription was a Christmas gift from my dad, but I’m enjoying it and will probably renew when the time comes.
I had a Popular Mechanics subscription for a while, but I’m not into working on cars (I just like driving/looking at/reading about them) so I was skipping 90% of the articles/info. Eventually I cancelled. I’d love to replace it with another car mag, but I can’t decide between Road & Track and Car and Driver.
Hmm…sounds like an IMHO thread idea!
We have a stack of Cooks Country on our coffee table.
Most adults who visit us flip through it - and then we are often surprised to be invited to go out to dinner shortly afterwards. Well, we at least pretend to be surprised…
My favorite, which was a surprise: Natural History. I got it gratis, as part of supporting a local life science museum. Highly recommended for anyone who likes the life sciences articles in NatGeo and Smithsonian (which we’ve also had). However, too advanced for most pre-teens. Keep it in mind for later, or get it for your own enjoyment.
As a kid, my dad’s business partner and his wife gave me this every year as a Christmas present. I loved it, and made a point to thank them in addition to the annual thank-you note. But on retrospect, it was mostly garbage. I remember cover after cover saying “How X will change your life!” … never to hear of X again. The article where the author recommends that cars have peaked fronts like the bows of boats, to reduce damage in a head on collision, without once mentioning the effect on side-on collisions. And on and on. At least, back in the lat 60’s and early 70’s, the editorial bar was very, very low. Maybe it’s better today. I suggest picking up a copy at the newsstand before subscribing. I really hope it’s better now! Maybe it would be fine anyway, for young kids: anything to get them thinking about things outside their daily experiences is good.
I was just lamenting the demise of the encyclopedia, and how every paper I wrote as a kid took far longer than it needed to thanks to finding so many interesting articles while looking for the relevant ones. Of course, online sources are a lot more convenient, and better for quickly jumping to all the related articles, but it’s not nearly as good for finding those fascinating things you weren’t at all looking for, which simply shared a common first letter or three. Pardon the tangent.
The New Yorker is a bit much for an 8 year old–although the idea is to have a reference library the kid can appreciate more as he grows. From earliest childhood, we had a New Yorker cartoon collection; it took me many years to understand the jokes about conservatives & liberals (can’t find it–a maid & butler fill another tray with cocktails & say “this is the round where they start to weep for the Spanish Loyalists”). Charles Addams was immediately understood…
However–remember that the magazine comes out every week! It will stack up awfully quickly. We also had an archive of* Life*–but that’s gone.
Today, National Geographic is the best. Especially the maps! That internet thingy will deprive many a silverfish of a happy home…
Kid’s magazines are covered! Highlights, Zoo Book…
Looking for something for me that will also spark their interest.
Muuhahahahaaahaaa!!!
Yes, as interested as I am, even if I do subscribe I probably won’t save those for long. I have a feeling that, pointing to a closet full of 635 issues when the youngest hits high school and saying “It’s The New Yorker! Cool, right?” Will be met with hard eye rolls 
Uhhh helloooo…Reader’s Digest!
When I used to spend time at my boyfriend’s house, 20 years ago, and I got bored, I’d go through his dad’s 1970s Reader’s Digests and read all the funny stuff.
I recently got a Readers Digest and was appalled how quickly I went through it. very little to read anymore!
A couple of quarterlies I’ve recently fallen in love with:
Oxford American
Bills itself as “the southern magazine of good writing” and lives up to it. Significantly higher quality writing and much more authentic than the whitewashed, mint julep fetishizing Garden and Gun-- about the best regional mag you’re likely to find outside of New York. There are occasionally more adult pieces, like dispatches from southern prisons and the like, but they’re typically pretty benign.
The other is Lapham’s Quarterly
It takes a theme-animals, magic, warfare, what have you-and traces every aspect of it through history via pieces from historical authors. The most recent edition, The Sea, had pieces from Melville, Homer, Jacques Cousteau, and a couple of contemporary environmentalists. It may feel a little academic for youngsters, but for the most part it’s quite accessible.
Another vote for Games magazine. We had a subscription from when I was ~7 to ~20, and there was always something for my taste and ability at each age.
Some good suggestions already. I’ll just add that Entertainment Weekly is worth reading. It (along with the SDMB) is how I keep track of what’s going on in popular culture without exposing myself to any more of it than I want to.
When I was a kid, MAD Magazine was how I learned about the world; but I have no idea what it’s like nowadays.
I also had a gift subscription to Popular Science in my teens through college; it was a good broad view of science and technology. I think I would also like Wired.
Too bad national Lampoon is no longer available.
My 10 year old loves Architectural Digest.