What: StumbleUpon is an online bookmarking site where users indicate their interests and the site introduces them to new and different Web sites. While "stumbling," users can save sites to their account, share with friends, or recommend a site, helping specific pages gain popularity virally.
"It's helped us grow traffic tremendously," notes Erin Ryder, PR director for LoftLife magazine. "It's been a great way to expand our audience, an audience interested in what we are writing about."
How: There are ...