The Website Slack World is pretty good. Although it is targeted for Slackware users, the Linux concepts are quite useful to other distro too.
For example, the fragmentation in Linux disks actually does not affect the performance, as much as MS-DOS systems. Here is the article in Slack World explaining why.
Anyway, there is only 3 online issue of Slack World so far, April,June and July 2005. Hope more to come!