Just say your keyword is "affiliate marketing" go to Google and search: affiliate marketing+blog or affiliate marketing+forum, that will bring up a list of blogs and forums about the keyword "affiliate marketing" where you can post your comments for link juice. Also get the SEO plug in for Firefox, just Google it, the SEO plug in when activated will show all do not follow links highlighted in red, you can also check PR and other stuff.
By talking about Blogspot as link sources, do you merely mean posting comments and then using them? That could be one part of link building but do not forget directories and article distribution.
Whether you use wordpress, blogspot or other flatform the ways on getting backlinks is just the same.
Make blogspot header, title, description sales oritend and keywords covered so it help u in rank and traffic.
Are you trying to look for blogspot sources? If yes, if I found one I just go to the blog roll of that and check on the links..
If you want to write blog posts that are good at attracting links from other blogs and websites, my advice would be to not use free blogs like blogger but to go with your own domain and wordpress. Then ping subscribers whenever you make a post.
you can make lots of tags in blogspot. Google will never report a problem in webmasters. So thats nice about blogspot. It works.
Submitting your blog to blog directories would be the best idea!.. Next is to comment on other blogs.. These will help generate traffic on your site..