After the official Google Blog, (the non-official first one of Aaron Swartz still in first position ;-) here the Yahoo Blog.
Whoupi doo! If you read it, you will see why I laugh a bit at this first post. A bit too much of self-congratulation. Bad PR from marketers who don't understand really what is a corporate blog ! It's not to proclame we are the best, the finest, blablabla, it's more in my mind to annonce new stuff coming up, get idea and interact with your customers.
Also note in the right column the "Industry Source"*. This is not a very good idea ! It will make jealous and it's not the purpose of a SE !!!
*PS: Note that 95% of thoses links are included in my RSS aggregator.