MindSpring Enterprises, an Internet service provider, has launched its residential high-speed Net access service in eight cities across the nation and expects to offer the digital subscriber line (DSL) service in three other cities by the end of the year. MindSpring has DSL resale alliances with BellSouth and Covad Communications. The ISP's high-speed service will cost $50 per month with a special $100 installation offer for a limited time.