try installing the firefox add-ons https://addons.mozilla.org/en-US/firefox/addon/321/ then search for your blog niche.
You can use a tool like fast blog finder or use dofollow search engines. I made a list of dofollow search engines, that might be useful for you.
All of the DoFollow blog search engines pull off of the same list. Why not go to the source...http://www.website-linkbuilding.com/list-of-do-follow-blogs/
I do use Firefox addon. This is the best tool I prefer to use to check the NOFOLLOW status of the links.
A couple of great tools to find do-follow blogs are "Fast Blog Finder" and "Comment Kahuna". Just google them. Fast Blog Finder has a free trial, and Comment Kahuna is free. In my opinion I like Fast Blog Finder better, but it does cost some money. They are both great though.
It just help you recognize which one is nofollow blog, you should use Google blog and add-on firefox together, that is my way.