I just found a list of PR5 blogs that use DoFollow so your posts and comments there will get you some link love.
http://www.toptut.com/2007/06/05/get-many-quality-pr5-backlinks-for-free/
The advice there is good too… “don’t leave a useless comment just for the sake of a link [snip]
You don’t need to leave your link in the body of the comment itself, in fact don’t do it at all, because it will either be filtered as spam or disapproved by the site owner for same reason. Inputting your link in the “website” field is enough, and then enter the desired anchor text in the “name” field. That’s all, the blogging software will do the rest of the work for you, and the link will be genuine, perfectly beneficial for both PageRank and Technorati Rank.
Cheers,
Gary
PS:
This too… three-easy-tips-to-seo-your-blog-post.