Below are the exact search queries for finding wordpress blogs, (copy and paste into Google Search, replacing "Your Keyword"): 1. site:.com inurl:blog "post comment" -"comments closed" -"you must be logged in" "Your Keyword" 2. site:.org inurl:blog "post comment" -"comments closed" -"you must be logged in" "Your Keyword" 3. site:.edu inurl:blog "post comment" -"comments closed" -"you must be logged in" "Your Keyword" 4. site:.gov inurl:blog "post comment" -"comments closed" -"you must be logged in†"Your Keyword" You can also use this free tool (www.dropmylink.com), It allows you to find a wide array of sites using your own keywords to get create content-relevant backlinks from.
I've got a suggestion to this: this kind of search is asking to ignore those sites where you must be logged in to post a comment. I used to avoid those places too, until I realized that the best backlinks come from those places where you must subscribe to post comments, it takes a little more time signing up, but it is worth the time you spend doing that because you get more quality backlinks to your site from those sites. A lot of comments I did in post-without-subscribing sites got lost, while at those places where I got an account to log in allways I get backlinks to my blog that are reported by Yahoo site explorer. Hope this helps!