It seems,we forget original topic of this thread and has started to discussion on "Penguin". Yes,of course, there are few link building techniques which would give quality backlinks to improve SERP and those are following:

* Social Bookmarking
* Forum Posting
* Article Submission
* Profile Creation
* Web Directories etc..

I believe that "SEO is battle of ranking and every SEO expert has it's own weapon to win this battle".

Originally Posted by ozsubasi View Post
I think that the over-optimization term should be forgotten now. It was a casual remark made by Matt Cutts which has since been clarified. There is no "over-optimization", there is optimization and there is spamming.
Anyway, what the OP was asking was not what not to do, but which off-page activities would be effective now. Do you have any positive suggestions that would help answer the question please?