As with any type of emulation, however, this is a drain on processing power and performance. So one of the biggest performance advances you can make on an Intel Mac is to get rid applications that are PowerPC native. Unless you're working with specific older applications, you should be able to manage this by updating your installed software, as most developers now offer Intel-native or universal binary applications. (The last major holdout was Microsoft Office, which now supports Intel processors with Office 2008.) You should also ensure any non-application executables like third-party preferences panes are also updated.
The second challenge Apple faced in moving to Intel CPUs was providing a mechanism, known as a universal binary, that would allow developers to offer a single application that would run natively on both Intel and PowerPC Macs. Universal binaries achieve this by including both the Intel and PowerPC native code. While effective for making application distribution easier for developers and users, universal binaries double the size of the code contained in an application.
The utilities mentioned in the previous tip can all be used to remove this excess code from your installed applications, slimming down your system. Don't expect all your applications to be immediately cut in half, however, as most applications include files beyond just code (files that define dialogs, windows and menu items, for example).
Note: If you have a mix of Intel and PowerPC Macs and you need to copy applications between them, you may want to skip this space-saving tip, since it will effectively create PowerPC-only and Intel-only versions of your applications.
3. Trim down iLife media libraries
Perhaps nothing takes up as much space on a Mac's hard drive as media collections. Apple's iLife suite allows you to maintain libraries for iTunes, iPhoto and iMovie that store your media; make them easy to search or browse; and make them accessible throughout Leopard and other apps. These libraries can take up a lot of space. For many people, however, simply culling material isn't a valid option, as that means giving up music, photos and video that you want to keep. Here are a couple of other options to consider.
First, if you have an external hard drive, consider relocating your media library to it. This will keep your media but free up space on your internal hard drive. This can be done with each library, but is probably most effective with video. While you may want your music and/or photos accessible at a moment's notice, that's probably not the case with your video library