A quick thumbs up for TipDrop as a site worth signing up to if you want to build some quick backlinks.
TipDrop is basically about sharing short amounts of information - tips - on anything you have some knowledge and expertise in. It also allows you to integrate your google adsense account to earn 75% of all ad revenue from your pages.
However the primary attraction of TipDrop initially is its great value for creating backlinks. Your profile page can include up to ten, yes 10, of your own links with title and description. I've barely done anything on the site - three or four tips to date I think - but Google has found my profile page and links. I know this because Google alerts for relevant terms I've set have been triggered. For ten backlinks TripDrop is worth and hour or so to sign up and set up even if you never do much else with it. If you share some tips and get a bit of adsense moola too so much the better!