The main blog in the field of language and linguistics. It's not very technical, in that most people can follow most of what they say without knowing the details of theories. But it's linguists, talking about what's actually going on out there in the world -- it's not self-styled grammar mavens moaning about how everything's going to the dogs.
From the web address I presume it's based at the University of Pennsylvania, though the Language Log site itself doesn't seem to refer to a home base. They have a wide variety of contributors, and carry a lot of weight in other language-based blogs I've seen. If you want one port of call to keep up with trends, this is it. A lot of it is just fun, some of it is serious discussion of technical matters, and a pleasingly large number of entries manage to combine both.
There's five to ten postings every day. It's not a collaborative thing, and unlike most blogs they don't even allow comments, but they do link to the linguists' own sites if you desperately need to tell them anything.
The main contributors include Geoffrey Pullum, a curmudgeon best known for his debunking of the Eskimo snow words nonsense, as well as being co-author of The Cambridge Grammar of the English Language; Mark Liberman; Bill Poser; Geoffrey Nunberg; Sally Thomason; and Arnold Zwicky. Because of their pre-eminence in the popular linguistics world, their ideas tend to be taken up. For example, the words "eggcorn" and "snowclone" will probably gain a permanent place because of the authority of Language Log.
It's a good place to find debunking of linguistic nonsense, and explorations of new patterns in language, and just plain curiosities. You get snippets about writing systems, about the history of ideas, about prejudices, about new computational techniques: and all with quick references to other blogs and websites.