What are these links to Digg, del.icio.us, reddit, Facebook and StumbleUpon that appear on BikeRadar pages?
They're called social bookmarking, and are a way for readers to collate and share links that they're interested. The sites, which are not associated with BikeRadar, are free to use although you will have to register.
For more on social bookmarking, see this Wikipedia article.
For more information about each site, try these links: