Planet13 - 3:51 am on Aug 10, 2011 (gmt 0)
What I have seen from my end is for less competitive niche, forum links can push previously unranked keywords to 2nd page at best. But not strong enough to make it to the 1st page.
The independent sites that rank in the top four or five spaces (they are ahead of the amazon, ebay, and ehow results) seem to have primarily a mixture of these types of links:
Articles on squidoo and other article sites
free / low cost directories (like $10 a year)
blog comments (mostly nofollow, surprisingly)
interlinking between sites
paid links (obvious ones)
They might have one or two good links that were naturally given (since the anchor text is generic), but that was about it.