The first blog that really made me sit up & take notice of how useful this whole blogging thing can be was James Enck's EuroTelcoBlog. At the time, he was doing equity research for Daiwa, covering European telecoms stocks, and writing pithy, controversial snippets that cut through a lot of the industry's B.S.
Unfortunately, he had to drop writing it a year or so back when a new employer's compliance department had less of a sense of humour than Daiwa's.
For reasons that James explains, that adventure has now ended. So he's now back in the blogosphere, and I for one would heartily recommend everyone here reads EuroTelcoBlog religiously.