The sites listed below work a little differently, so please read the brief descriptions below of the three sites we feature on our article pages.
Each site requires you to register if you want to start submitting links or to vote on other people's submissions. Registration is fast and free.
Once you have registered with one or more of the social-bookmarking sites, simply click on its logo or name in the "SHARE" box on any National Geographic News article, photo gallery, or video to submit that page to the bookmarking site.
About Selected Social Bookmarking Sites
When you submit a link to the Digg site, other Digg users can either "digg" (vote in favor of) or "bury" (vote against) your submission. The site ranks links based largely on how many digs they receive.
Any registered user can post comments on any link submission. Debate is often lively and not always for all ages.
StumbleUpon requires you not only to register but also to download a free software plug-in for your Web browser.
The software adds StumbleUpon buttons to your browser. As you surf the Web, you can click the "thumb up" button to vote for the page your—or the "thumb down" button.
Gradually, StumbleUpon's computers form a sharper and sharper idea of what you do and don't like. That's where the "SU" button comes in—click it and you'll be taken to a random page that StumbleUpon's computers think you might like.
Each time you click the StumbleUpon logo or link in the "SHARE" box on a National Geographic News page, you're casting a vote in favor of that story.
Like Digg, Reddit allows you to submit links you like and to vote for and against others' submissions. Reddit will also suggest sites you might like based on your past votes and submissions.