iStumbler is an easy way to scan for information about the Wi-Fi environment around you, as well as see available Bluetooth devices, and what Bonjour services are available on the local network. The latest version, release 99, works only with Mac OS X 10.6.2 or later, adds support for the 5 GHz band used by 802.11a and 802.11n, and takes advantage of the coordinate-based location feature in Snow Leopard to allow GPS-like tracking as the application scans. (Free, donation requested, 1.1 MB)
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Use Shift to Compare Edits in iPhoto '08
In iPhoto '08, while you're editing a photo, press the Shift key to see a "before" view; let it up to see the "after" view. It's much faster and easier than using Undo and Redo.