There are a number of other geoscience-oriented blogs out there.
One list is at the German site geoberg.de.
I discovered a relevant blog there today, the Berkeley Seismo blog. Looks pretty good, don't know how I missed it up til now. But since our blog here is northeastern U.S.-centric, I think we can co-exist.
I've kept my own blogroll on the left minimal, to include blogs more related to earthquakes and seismology, that are regularly posted to, and professionally oriented. Am I missing any of your favorites?
But I'm not yet ready to start twittering. I'm with Gary Trudeau/Doonesbury on this one, so far.