This image is from Look Before You Leap with a Business Blog at Word Sell, Inc. Another useful resource is a 2005 Business Week article -- updated earlier this year -- describing the trends and potential of blogging for business.
If you want to start your own blog, you can use templates from Wordpress or Blogger.com. I've been using Blogger (a division of Google) for some time and the system is quite easy to adapt -- you can if you wish structure things so the blog runs off your own website with your own domain; but you lose some of the template convenience in exchange for brand purity (a limited advantage, I think, which is why I haven't worried about it.)
The question, then, is what do you do with the blog template to make it work. I've found a couple of resources that could be helpful. Chris Garrett's Authorityblogger.com has useful insights and materials. And The New Rules of Business Blogging by Linas Simonis provides some useful insights. (I'm breaking some of Linas' rules with this blog's frequency, but enjoy it, so there.)
Your main restraint -- and challenge -- in business-focused blogging is to combine the interests of your business with some real personality. You can't just hand this work over to the PR of communications department, so if you are not naturally a good writer, you might find blogging is not right for you. Great blogs combine passion with useful information.