I started to do link building again for various sites and blogs. Searching for DoFollow sites is hard if you don’t know where and how to start. First I tried to find the sites what have “CommentLuv” plugin installed. After I tried to find directories with dofollow blogs and sites, and I found several like DoFollow.us and Links DoFollow.com. Anyway if you are interested to find such sites, a simple search on Google is not enough. Each sites is pretty unique from this point of view, and even if a blog is nofollow free, is very possible to have a limit of minim X comments until it will do your links dofollow.
Also if you want to check a site if is nofollow free you can use NoFollow Firefox addon from here https://addons.mozilla.org/en-US/firefox/addon/nodofollow/ . NoFollow Addon is helping me to see (is highlighting the links with blue if is do follow and red if is nofollow) if the sites is using nofollow on comments or not.
Do you want to reward your commenters from your blog? Then use CommentLuv and Show Top Commenters plugins in wordpress.