There's a new compilation of 100 Earth science blogs posted online, including quite a few I haven't seen before. The definition of Earth science here includes meteorology and climatology so it's broader than many. The list is sorted into categories such as geology, paleontology, volcanology, geo-hazards, mineralogy, and planetary science.
[Update 2-18-13: the owners of the compilation site notified me that they are in the process of redesigning their site and will be taking down and making significant changes to a lot of their content, so the link currently up will potentially be inaccurate or broken as a consequence. As an alternative, I recommend Geobulletin, the geoscience blog aggregator at http://www.geobulletin.org/]