Whether or not you have your own blog, you can still use blogs to promote your business.
A case in point: I recently ran a blog PR campaign in association with Steve O'Keefe for Wiley Publishing, to promote Alan Dershowitz's new book The Case for Peace.
I contacted 34 Jewish-interest blogs (plus two sites that I thought were mission-critical even though they aren't blogs). For each blog, I commented on a relevant post. Where I thought it was inappropriate--or potentially incendiary--to intrude with a comment, I sent a pitch letter to the blogmaster offering a free review copy. Most of the blogmasters wrote asking for copies. And (thank Heaven) no flames!
You can see some of the results if you Google "dershowitz peace mordechai schiller".