If you are truly speaking about a "Post", then the answer is certainly a resounding YES! If you are speaking about comments, then not so much. Most comments have no-follow tags with their links. That is on top of the fact that many comments are deleted quickly. Classic example of links from blog posts are within my Antiques News site listed in my sig.
I think that liking to your site/blog in other related contents blogs help your site/blog. For me I try to search for related blogs like mine Mesothelioma settlement and make some good posts.
You aren't thinking outside of the box if you can't find dofollow blogs.... http://www.bumpzee.com/no-nofollow/ 689 blogs there should keep you busy for some time. Good luck
Traffic, and possibly SERP. Not bad is it? Nofollow is mainly for Google, and even then it's mainly for not passing Page Rank. By many accounts MSN and Yahoo both flow freely through the link, and there even has been a few people that claim googlebot passed through such links. (I personally don't know). Either way though, Traffic is, or should be, the driving force behind any site, and the higher the quality of that traffic, then the better. Finding ANY popular blog, nofollow or not, should be beneficial. Just make sure you don't spam... or all the SE's will make nofollow something standard.