I just added a paragraph to my site in which I beg for links from my users...underlining that it is a free service that provides independent information of the sort they won't find in other places, so if they appreciated that sort of info, "they" (meaning users that happen to have a blog, website, etc.) should refer others to it.
Not so sure whether this will have any effect at all, but at least I'm amused about the whole thing.
I have forms for my users to submit unique content to my site, in addition to recording links they have developed into my site. They get points for doing so. A good inbound link gets them more points then a drawing, but less than a fiction or review.
Basicly I have turned my users into content submitters and link monkies. In return, they get points which can be redeemed for product they enjoy.