Blogging is one way you can get backlinks. This is a quick way and there is no limit on the number of link you want to create. Here are two popular ones wordpress.com blogger.com Please add more ...
Those backlinks would be useless without pagerank, though. You can't just create a blog and link to your site expecting SERP benefits.
Agreed... It will be from 0 pageranks ..similar to what you get from the sig backlinks. However, you can put as many backlinks as you want - may be 10 or 15 ... livejournal.com is another.
Commenting on dofollow blogs is a much better way of getting backlinks because there are plenty of high pagerank dofollow blog pages out there. You should try that out instead.