Light aircraft fly fairly low and often without ground control, so they sometimes lose their way in bad weather. Digital Avionics Corp., of Marietta, Ga., has developed a system that shows pilots microfilmed map, detailed down to the power lines. The map adjusts as the plane changes direction.Digital plans to sell the system for $8,000, beginning next year, and has found an unexpected market in low-flying helicopter pilots.

His girlfriend's compulsiveness led Marc Sauve to design the trash can for the '80s. She wouldn't throw away the plastic shopping bags that the supermarket packed her groceries in. Instead, she tried to use them for trash by hanging them on doorknobs. So Sauve fashioned a chrome-plated bracket to hang on the inside of a cabinet door, creating a trash can. He later designed a freestanding holder.Now Sauve's company, Marco, in Dallas, is selling the holders, which retail for $3 to $5, in supermarkets that are eager to give customers a new reason to accept the plastic bags.

As a dog breeder, Gene Weakley learned how hard it is to ship an animal somewhere -- one airline even lost one of her dogs for 10 days. So Weakley started Professional Pet Travel Service Inc., of Memphis, to make sure traveling dogs and cats get to their destinations. She arranges itineraries and kennel services and sends agents to airports to pick up pets or put them on connecting flights.

A start-up can redefine its market many times before it sells its first product. Advanced Polymer Systems Inc., of Redwood City, Calif., started out to make microscopic polymer spheres for testing water purity. Along the way, the company discovered more promising uses for the spheres. It began work on a test for syphilis. Then it discovered its main product -- porous spheres that hold and gradually release such substances as perfume or insect repellent, thus enabling manufacturers to offer so-called longer-lasting products.

Every year 69 million Americans suffer from nasty home injuries. But not many people have just the right supplies on hand or know how to administer first aid. So Stephen Kowal and Peter Coughlan started Reed Products Inc., in Newburyport, Mass., to sell four first-aid kits for specific injuries: wounds, burns, poisonings, and eye traumas. Each $5 kit includes supplies and treatment instructions.