Some interesting content has been cropping up lately as KML:

• Anthropogenic biomes are “globally-significant ecological patterns within the terrestrial biosphere caused by sustained direct human interaction with ecosystems.” Now you can see what and where they are on Google Earth, Maps and Microsoft Virtual Earth. (Give the layer some time to download for a given view.) Made with Arc2Earth!
• The US Environmental Protection Agency now georeferences its emissions measuring stations and puts them into a KML layer. Download everything or just the region and the pollutant you are interested in.

Meanwhile, some other tools keep on improving:

• Version 3 of the open-source content management system Plone is now supported by PleiadesGeocoder, which lets you georeference Plone objects. Thus writes Sean Gillies at Import Cartography.
• Favorite Mac GPS GPX/KML uploader/downloader LoadMyTracks gets Leopard compatibility.
• World Wind’s KML support now includes timeline functions.