General Help
"As Mac OS X users know, HyperCard requires Classic Mode. But with the arrival of Leopard, Classic Mode is no more [...] If you've worried about losing data you've accumulated in HyperCard stacks [...] you can use HyperPort before you upgrade to export the data and then import it into your choice of nifty current Mac OS X applications."
On application extensibility: A very thoughtful article about the reality of customizing applications, how plugin hooks are more important to this than open source, and how this relates to OS X.
Lots of good information on system setup here
This is an extremely useful article on various ways to schedule tasks for automatic, periodic execution. It's specifically for MacOS X 10.3 but applies in some degree to earlier versions as well.
Exploring the Mac OS X Firewall: Useful article on doing more with the firewall built in to OS X.
Panther Maintenance Tips applies in some measure to all versions of OS X. MacOS X Tips and Tricks - unix tips, Midnight Commander, extensive discussion offink, etc.
"Resources and information about Mac OS X and its BSD underpinnings".
Mac OS X for UNIX Users: A pdf from Apple with a lot of interesting information about the design of OS X, apart from its relevance to unix.
Mac OS X Hints - Make utility Terminal windows less intrusive.
Balthisar's Guide to Non-PostScript, Network Printing for Macintosh OS X This package contains a detailed paper explaining how to use Ghostscript to convert the postscript output of any program into a file that can be transmitted to the printer to get an image - full of useful information.
Cocoa Gestures: control programs with configurable mouse gestures.
The Boot Process: Useful documentation from Apple, including tables of daemons and startup items.
Here are some practical notes by Charles Maurer on color matching for digital photography, published 4 Oct. 2004. This is an excellent techinical overview of OS X.Install Quicktime 7 but keep Quicktime 6 Pro: If you have Quicktime 6 Pro, and want to upgrade to QuickTime 7 without losing your Pro features, you can.
Use Google Maps with the Address Book Widget
Tiger Secrets: System settings: An article in MacWorld covering a handful of obscure tips and customizations for Mac OS X 10.4.x.
The Power of mdfind: Here is an article about the CLI interface to OS X's Spotlight.
Customizing the Cocoa Text System: A detailed and very useful article covering keybindings and input managers. Learn how to make your keyboard automatically create html tags, search for text, move around in a text field, and much more.
"Mac Geekery is a place where more advanced users of the Macintosh hardware platform can get together and share tips[...] without fear of the user level of the recipients. If you have an article you've been dying to write up but can't 'dumb it down' enough to be mainstream, post it as-is here."
When 'Smart' Cut-Copy-Paste Attacks: John Gruber notices some interesting things about editing in Cocoa text views.
Mac OS X: What Are All Those Processes?: "Mac OS X (like any unixish OS) always has a number of things going on in the background -- processes that take care of business behind the scenes. [...] you may wonder what on earth they're all there for. This list is here to answer that question."
Mac OS X Internals: A Systems Approach: A much-anticipated book by Amit Singh that "describes the architecture and design of Apple's operating system. The book is targeted at anybody who is curious about Mac OS X and has a system-level interest in operating systems. At a very high (and simplistic) level, I expect this book to appeal to both those who use Mac OS X, and also those who do not."
Sharing, Syncing and editing iCal over WebDAV: A "cheap and dirty" solution.
Turn Your iPod into the Ultimate PowerPoint Accessory: This tutorial explains how you can put your Powerpoint, Keynote, or PDF presentation on your iPod, connect it to a projector, and run a presentation with it.
DVD Software Backup: Nowadays software often comes to you on a DVD. You paid for it, and it's a good idea to make a backup copy, but you might not know how or may be under the impression that you need to buy more software to back up the software you just bought. Here is a simple solution from macgeekery.com
Create streaming flash video: This seems to be (I haven't tried it yet) a very useful set of notes on how to use "open source or other freely available tools" (ffmpeg, flvtool2, and mencoder) to convert your DV or other video to streaming flash, which is very widely supported.