Personally, I find this site to be the best resource I've found for the PPC. Every once in a while I pick up a copy of Pocket PC Magazine, hoping there will be something interesting, but 99.9% of the time it is all information I read here a month or more before.
There is a British magazine that I sometimes find on the shelf at my local bookstore - I think it's called PDA Essentials - that covers both Palm and PPC. They have tutorials on various topics in each issue and every so often there will be one that is worth picking up.
I remember Compute's Gazette well. I spent many hours entering endless lists of numbers into a program called MLX or MLM or something like that. For a real walk down memory lane, try a
C64 emulator on your PPC. I get a kick out of just seeing that blue startup screen again after all these years.