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Are you looking for a shortcut to better rankings in the search engine results pages? Are you trying to increase PR to a web page?
Instead of seeking to exploit one thing in order to gain something else, try creating unique and valuable content of your own.
This attitude of using unrelated pages, forums, blogs, directories as a method of SEOing is wrong and generally ineffective in a long term web site promotion strategy. In fact, these behaviours are not a part of search engine optimization at all. Most of SEO involves on-site elements. I don't care what other SEOs think. There is a big difference between crafting quality content and seeking to artificially empower it; one is SEO the other is spam.
Try not confuse a search engine optimizer with a linking strategist. They are in separate classes.