Point of Interest You'll definitely need a map for this entrepreneurial adventure.

As a startup business, it's sometimes tough to know where you're going. But Allen Tsai and other online entrepreneurs who use new mapping technology make it their business. Tsai, 27, is the founder of CellReception.com, a mapping website that locates cell reception, towers and dead spots across the country. "Cell phone reception was and still is widely variable," says Tsai, who launched the site in 2003. Other websites mapped only bits and pieces of tower locations, and the FCC's tower registration database was just a "chart of coordinates," says Tsai. "It wasn't very useful unless mapped. So that's what I did."

CellReception.com links to Tsai's other website, Mobiledia.com, an educational resource on the cell phone marketplace. Tsai said he did this to increase traffic and boost visitor comments about cell reception, which add value to the coordinates Tsai maps. Today, CellReception.com gets more than 90,000 visitors a month, and the sites earned combined sales of more than $1 million in 2006.

Tsai clearly went in the right direction with his business, but can other entrepreneurs find opportunity on a map? Virender Ajmani, author of upcoming Google Maps Mashups, thinks so. Online maps have been created to help visitors find cheap gas, monitor local crime, avoid road work and much more. Ajmani sees a lot of growth potential for real estate sites, which could show landmarks, freeways, schools, grocers and other surrounding points of interest to buyers and sellers.