Apple has released Aperture 3.2.4, which promises improved stability for the professional photo organizer and editor when running on Mac OS X 10.6 Snow Leopard. The only other item noted for this maintenance release is a fix for an issue that prevented the Viewer from updating correctly after editing a photo using an external editor. ($79.99 new in the Mac App Store, free update, 635.54 MB)
Go Back and Forth Fast in Preview
If you're reading a PDF in Apple's Preview software, and you follow a bookmark or an internal link to move around within the PDF, you can quickly return to where you were by pressing the keyboard shortcut Command-[ (that's Command-Left Bracket). Or, you can choose Go > Back.
The command works iteratively, so you can go back to just the previously viewed page or if you issue the command again, to the page before that, and so on. There's also an equivalent Go > Forward (Command-]).