Virtualization software VirtualBox has been updated to version 4.0. This major release reorganizes the software into a base package with numerous Extension Packs. The interface has been reworked significantly, and new virtual hardware has been introduced, too. Detailed release notes are available at the VirtualBox Web site. (Free, 79.2 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-]).