If you’re interested in following some of the key blogs on a particular topic, such as news, marketing, or tennis, for example, All Top is a good place to start.
For each topic, All Top displays some of the key blogs on that topic. Under the title of each blog, they list the titles of the five most recent entries. If you display your cursor on the headline, you’ll get a preview of the story, and you can decide if you want to read it, click on the title. Click on the domain name to go to the home page of the site.
I checked out their list of marketing, pr and social media blogs. A number of the blogs they listed were ones I’ve included in my blogroll. However, there are also a number of “must read” blogs which they haven’t yet included. So although it’s not a comprehensive list, it’s a good place to start if you want to find blogs on a particular topic.