Apple's Mac Pro Audio Update 1.0 for early 2009 Mac Pro models comes only with terse release notes, stating that the update "reduces processor utilization during audio activities such as playing or recording music." More information regarding installation steps is available on Apple's Web site. The update is available via Software Update and the Apple Support Downloads page. (Free, 1.64 MB)
Spacebar Magnifies Photos in iPhoto '08
In iPhoto '08, you can choose whether double-clicking on a photo will edit it or magnify it. I prefer my double-clicks to edit photos, but every now and then it's nice to magnify a photo. To do that, even when double-click is set to edit, just select the photo and press the Spacebar.