Mac OS X, as it ships or gets installed from an Apple DVD, is a mighty impressive operating system, but different people use it in different ways.
While many people will never even think about modifying the behaviour of their systems, there are many more who will want to do exactly that. If this is you, you'll be interested to learn that there are a large number of excellent tools for tweaking OS X and altering the way it works, the majority of which operate non- destructively.
There are also some great monitoring and system maintenance tools available that go way beyond what Apple gives you as standard, and these can help you on your way to keeping a clean and healthy operating system that lasts a long time. Here are some of the best.
Freeware, Mac OS X 10.4+
You may not be aware that your Mac contains many logs and sensors, most of which aren't immediately accessible without help. This help is available for free in the form of iStat Menus, a program that puts eight configurable menus at your fingertips in the menu bar. These menus will monitor crucial parameters such as CPU usage, disk activity, network traffic, temperature and processes. For troubleshooting, or simply a better way to understand the workings of your Mac, iStat Menus is an invaluable tool, and you needn't be a technical whizz to use it successfully.
Freeware, OS X 10.2+
OnyX is a comprehensive system-tweaking and maintenance tool that gives you unprecedented control over the way your Mac behaves and displays windows, buttons and menus. It also contains extensive cleaning commands for clearing caches and logs, repairing permissions and running maintenance scripts. OnyX puts these commands at your fingertips. One particularly useful option is to view hidden files and folders, which can be crucial for troubleshooting
Freeware, Mac OS X 10.2+
There are many small applications that will monitor your Mac's core functions and activity, but of all these tools, MenuMeters is the most compact and unobtrusive one we've used. Controlled via a Preference pane, you can activate monitoring of CPU, network, disk and memory usage, and these will sit quietly in the menu bar, letting you see at a glance what's going on. A simple mouse click will display expanded statistics.
$10, Mac OS X 10.3.9+
Mac OS X 10.4 introduced widgets that are pretty cool, but they have to be "invoked" and seem to live not on the Desktop itself, but somewhere above it. If you'd like to alter this floaty state of affairs, a dedicated application will let you do just that. Amnesty Singles is a program that enables you to convert widgets to standalone applications, simply by dropping your favourite widget onto the program and clicking a button – it's that easy. This turns any of your widgets, be it Dictionary, Calendar or Ski Report, into mini, standalone applications, making them much more flexible.
Freeware, Mac OS X 10.3+
If you ever have to rename more than a couple of files at once, you'll realise what a tremendous pain it can be as you click in their name fields over and over again. Renamer4Mac is an excellent free program which lets you batch-change filenames in many ways, including search and replace text, insert/overwrite, number files and convert upper or lowercase. It's an incredible timesaver.
Freeware, Mac OS X 10.3.8+
Modern Macs incorporate multiple temperature sensors, and this program is able to read them and provide you with a real-time display and graph of how hot each part of your Mac is getting. While Temperature Monitor doesn't actually modify your system, it can be key to identifying trouble spots within the computer or working out where best to position the Mac in the room for optimum temperature and performance.
$20, Mac OS X 10.4 (not OS X 10.5)
ShapeShifter is a program that lets you radically change the appearance of Mac OS X right down to the core – windows, buttons, scroll bars, and pretty much everything else can be "skinned" using freely downloadable themes, some more outlandish than others. The original graphic elements are kept safe, too, so you can revert back at any time, but it's not recommended for the faint- hearted nevertheless.
$13, Mac OS X 10.4+
Although OS X is infinitely better than Windows when it comes to installs, apps can leave libraries, preferences and caches dotted around, so trashing the app isn't always enough. AppZapper tracks these rogue files and shows them to you so you can safely delete them. It's a good way to try out programs and delete them totally afterwards.
$10, Mac OS X 10.3.9 or 10.4 (not 10.5)
Windowshade X is one of the best third-party solutions for managing windows. A double-click can reduce a window to its title bar, Minimise in place makes the window tiny but viewable, and a third option renders the window almost transparent.
Freeware, Mac OS X 10.3.8+
TinkerTool allows you access to a large number of hidden preference settings already present in OS X but which Apple ordinarily hides away. You can customise the appearance and behaviour of Finder and the Dock, the format of screenshots, turn off Dashboard, and a host of other useful settings. It's all non-destructive, so you can easily reset the original settings.
$29, Mac OS X 10.3.9+
DragThing is a quick launcher which combines features from the Dock and Finder to provide quick access to documents, folders and applications. With multiple configurations and support for hotkeys, it stores frequently used items and lets you paste them into apps. It also allows application switching and the possibility to move the Trash bin to the Desktop.
Freeware, Mac OS X 10.4 , limited functionality on 10.5
Quicksilver is a slick add-on for OS X. At its simplest it's a launcher, providing a way to launch any program or file at a keystroke, but it's actually much more than that. You can install application-specific modules which give you new actions based on that app, plus the ability to upload, rename, move, open and manipulate items from its floating interface.