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)
Keep Markup Tools Active in PDFpen
By default, PDFpen switches back to the Edit tool each time you add text, scribbles or other markup. To keep a tool selected (continuous use mode), double-click it. To exit continuous use mode, click the Select tool or press Command-1. You can also make continuous use mode the default by selecting Keep Tools Selected After Use in PDFpen's Editing preferences.