Casting the digital equivalent of a message-in-a-bottle into the Internet’s vast sea of content, many people start Web sites or blogs hoping that they will find an appreciative audience for their precocious parrot videos, cupcake recipes or pithy commentary on everyday life. The dream, of course, is that they will develop a large and loyal following — and potentially profit from it.

While most of these self-publishers don’t attract the attention of anyone other than indulgent family and friends, there are those who find wider recognition and some income. What the successful have in common is a passion for their subject and a near-compulsion to share what they know. Advertising, merchandising, offline events, book deals, donations and sometimes sheer luck also play a part.

“My advice is to choose a topic you’ll never get tired of,” said Stephanie Nelson, 47, of Atlanta, a homemaker who founded CouponMom.com in 2001 to share tips on saving money by using coupons. “The first three years I made no money at all, so I had to love what I was doing to keep going.”

Ms. Nelson said her Web site now has more than 3.8 million visitors a month, and the income it generates supports her family of four — allowing her husband to retire early from his corporate job five years ago. “I’m still not tired of it,” Ms. Nelson said.