Linux Magazine is pretty good. I'd say it's a mix between more basic stuff and some advanced articles such as one on using Ganglia for cluster monitoring that was in the last issue I bought. You're as likely to find an overview of the new features being put into the 2.6 kernel as you are to get a detailed article on gcc and refining code to get less compiler error messages.
Linux User and Developer is another one I've gotten a few issues of. I'd say it seems to focus more on the eye-candy and reviews of such of various distros or software. A bit more like a conventional magazine, but in my view a little bit expensive and full of spelling and grammar errors. It certainly has some very good detailed articles as well, but I was a bit dissapointed by a few weak pieces in the last issue. It's also based out of the UK, so perhaps that has something to do with the hefty price.