Well, Polyhedron appears to be dead...once again...so you may be able to scratch it off the list.
Poly was originally the RPGA's magazine, and a subscription to it was included as part of your RPGA membership dues. Around the time the RPGA went to a free-membership setup (2002), Poly was discontinued.
It reappeared, not too long later, as the "backup feature" in Dungeon. Poly would feature non-D&D d20 content, including "mini-games". Vocal dislike of Poly among a large number of Dungeon readers led to the discontinuation of that experiment.
Poly was resurrected, again, last year, as an e-mail-only magazine sent to RPGA members. I think there were about a half-dozen issues or so before it went away again, very quietly.
Other gaming magazines I can think of off the top of my head:
- Knights of the Dinner Table -- originally just a gaming comic, it now contains quite a lot of RPG content, though it's focused on HackMaster.
- InQuest Gamer -- focuses primarily on collectible games, though they had RPG content for a while (and still might; I haven't picked up a copy in a year or two)
- White Dwarf -- focuses pretty much exclusively (I believe) on Games Workshop games
- Pyramid -- Steve Jackson Games' weekly e-mag, it was once a print magazine.
- Journal of the Traveller's Aid Society -- SJ Games also puts this out, an e-mag specifically supporting Traveller.
If memory serves, Palladium publishes / published one (Rifter?), though I have no idea how often, or if they still do.
I know I'm not remembering several more that are currently in print, too.
And, as long as I'm at it, a few that I, personally, mourn the passing of:
- Star Wars Adventure Journal
- Star Wars Gamer
- Scrollworks
