eBay and Brides magazine are running a "Build Your Bling" contest with the opportunity to win a diamond ring worth up to $25,000. Participants can register at diamonds.ebay.com and customize and upload their unique ring design in three simple steps, and are then encouraged to share their design with friends through social networking sites.

The contest's Share function links to over 50 social media channels including Twitter, Facebook, Flickr and MySpace. Since the winner of "Build Your Bling" will be determined by public poll, contestants are motivated to spread the word. Voting is open through February 19. On February 26, the winner will be announced on diamonds.ebay.com, and two runners-up will be awarded an eBay gift card for $100.

The eBay Diamond Ring Designer home page will feature content from BRIDES magazine, including daily tips on topics including proposals, engagement and weddings from Editor-in-Chief Millie Martini Bratten, and insight on diamond ring design and trends from Beauty & Jewelry Director Denise O'Donoghue.

"The Diamond Ring Designer underscores our commitment to innovate across the Marketplace, using technology to develop and deliver an exceptional shopping experience," said Lorrie Norrington, president of eBay Marketplaces. "Through diamonds.ebay.com, we're bringing quality, selection and value to the online diamond buying experience, enabling savvy shoppers to design and purchase exquisite diamond rings with confidence and convenience."