You know if you want to get backlink, you look for pagerank. But how can we find blogs that have pagerank? Thanks.. @Yusuf Ali Bozkır
You can do this by installing different SEO addons like search status or seoquake and after that type your target keyword in Google and it will show everything you need.
Yes, I also have tried seoquake. It is a great tool to find blogs with PR. Just type your keyword, you will see PR in Google listing page.
There are a lot of ways to search out good page rank blogs, blog directories, online tools can help you to find out your business relevant blogs for blog commenting.
If you use Safari, you can install the SEO Book toolbar or SEOquake. It shows you the page rank of every page you visit so you can check out the PR of the blogs you visit. I hope that helps you.
Popular blogs/sites usually have great Pagerank and you will get the best of both worlds since you will get a boost of traffic and a nice backlink as well. Now back to your main question on how to find them. Honestly go to google and type in most popular blogs and you will find a list of different blogs you can check out. Then from these blogs they usually are linking to other popular blogs that are part of the community and so on and so forth and it will not end. And yes it is that simple you can thank me later!
Don't get so obsessed about page rank. Research a site in http://www.opensiteexplorer.org to find out its domain authority (read more here: http://www.seomoz.org/learn-seo/domain-authority). Focus on site quality (such as whether the content is good, frequently updated, etc), rather than a meaningless and easily to manipulate number.
If i want to get blogs that have pagerank all you need do is type the pr you want example 'pr4 blogs' and search on Google.