The current research in mobile agent systems has demonstrated the utility of this paradigm in building a wide range of distributed applications and systems. In this paper, we present the promising areas for mobile agent based applications. These range from network management, to personal assistants over the Internet, to distributed collaborations. There are many mobile agent programming platforms available today. A large cross-section of these are based on Java. The design of a mobile agent programming platform requires addressing several important problems. In this paper, we discuss these design issues and show how some of the contemporary mobile agent systems have addressed these in their designs. We focus particularly on the Ajanta system, which is a good representative of modern Java-based agent programming platforms. We present here two applications developed using Ajanta, and we discuss the future challenges for research in this field.