If you aren't already subscribed to LWN (lwn.net), do it now. It is the single best resource there is of both Linux and the broader UNIX ecosystem, both technical (I know a lot about LRU lists that I didn't before) and the broader social movement (I know much more about the governing models of various projects and their community engagement than I did before).

There is a fee but it is lower than for any paper trade magazine and the quality is absolutely on par with such. They have a staff rather than taking articles from anybody which I feel helps keep an even quality to the writing. Absolutely recommended.