Since the demise of Dragon and Dungeon magazines, at least in actual printed format, I have been constantly searching for other print gaming mags. To fill the void I have found a few magazines that stand out.
Fight On!: I have only read the first issue, there are only 2 released thus far, but I like it. The mag has a very old school feel, content that can be used in most games and it is available in pdf or print versions.
Polymancer: A good magazine put out by Polymancer Studio with lots of generic content that is usable in most games. Most of the articles are not only funny but very well thought out. The company did have some hacker problems a while back and the site is still being reconstructed, so you may find some dead links.
Signs and Portents: This mag is to Mongoose Publishing, what Dragon magazine was to D&D. It basically gives material for games published by Mongoose and if you play them it is probably a great read. I don't generally play Conan, or Babylon 5 so while the content looked solid enough, there wasn't much there to my liking. It is free to download in pdf.
Rifter: This is Palladium's version of Dragon magazine. Every issue seems to have a theme or focus on a particular setting/game, but since the Palladium system is used for all their games the content is mostly useful no matter the Palladium game you play. Since I have a fondness for Rifts I do like to pick this quartly mag up when it comes out. Other than issue #0 of Digital Rifter, the only downloadable issue, all the issues are print and can be ordered individually or as a subscription.
Digital Hero: "Digital Hero is a bi-monthly e-zine for all aspects of the HERO System." I have never actually read an issue of this and can not comment on the quality of the content, as I do not play the Hero system... yet. You can buy it as a single download or as a subscription, though I think the subscription option may be a moot point. I have heard that the magazine has been cancelled, but back issues are still available.
Kobold Quarterly: I have never read an issue of this magazine but have heard nothing but good things about it and have just ordered an issue. This is another generic content magazine that is meant to fill the void of Dragon and supply useful content to fantasy gamers. Every time I have gone to the site it seems to be down or have some type of technical problem, but you can buy issues at Paizo's store.
Knights of the Dinner Table: This gaming magazine/comic book put out by Kenzer & Co. is my all time favorite. Not only do you get great article by Ken Newquist (Nuketown) and Mur Lafferty (The Murverse) there is also some really good generic content, content for Kenzer & Co. products and the best, IMO, gaming comic around. Definitely worth checking out. I think a free downloadable version of issue number 132 is still available somewhere on the site.
Pathfinder: I have only read one of these and they do provide some really good generic D&D content. What else would you expect from Paizo? Now that Paizo has adopted and "fixed" the 3e D&D rules the magazines will apparently be switching to official content for their Pathfinder system.
Dragon Roots:Billed as a "Magazine for Gamers by Gamers" according to their site. They actually came to my attention just the other day due to their connection to the "4e killed Gary" t-shirts. They claim they had nothing to do with them and I have never seen one of the shirts, so I don't know if they exist. Having added them to the list at the last minute, I have not had a chance to read one of their issues. Though I do see that pdf and print versions are available.
I have also found a really good fantasy fiction magazine called Black Gate. While it is primarily a short story mag, there are actual articles in it as well. The Summer 08 issue I picked up, issue 12, has an interesting article about solitary RPGs which was worth reading. There is also a Knights of the Dinner Table strip on page 222.
I forgot to mention that Black Gate is allowing people to preview issue #12, the one I bought, by downloading the entire issue for free. Download Issue 12
Just scroll down the page and in the left hand side of the scree you will see Download Black Gate 12 free. Click and you got your free pdf issue.
Here are some other fantasy &/or sci-fi magazines that I recommend checking out:
Fantasy & Science Fiction
Realms of Fantasy
Analog: Science Fiction & Fact