DDJ and CUJ (C User's Journal) were two very good magazines that I used to read a lot. BYTE (more so in its earlier years) was another one on the same lines. Can't forget some of the regular contributors to BYTE, for example (and I don't mean just Jerry Pournelle, though his column was entertaining too). Heck, I used to read Steve Ciarcia's Circuit Cellar column out of interest, even though I was not into electronics. So well done, the articles, the photos, etc. I still remember, in one of the first BYTE issues that I read, a very good introduction to Huffman coding by Jonathan Amsterdam. And so many other such good articles, in all three of those magazines ...
Back in the 80's DTACK Grounded and Micro Cornucopia, then later Computer Language and DrDobbs (remember those Cauzin soft strips?). Now I just depend on HN posters to TLDR stuff for me unless a subject really grabs me.