Agents provide a new paradigm for developing software applications that involve delegation of tasks and responsibilities to computer systems. An intelligent agent is an autonomous, proactive, utility-maximizing entity that can, given user preferences and goals, autonomously plan and execute actions to achieve those goals effectively and efficiently. In this talk we will present overviews of some theoretical issues and practical applications involving intelligent agent systems that we have been investigating at the MultiAgent SysTEms ReSearch group (MASTERS) at the University of Tulsa. Theoretical frameworks to be presented include technologies that allow peer-level agents to negotiate agreements and resolve disputes. Application topics include technologies enabling the development of robust recommender systems and mechanisms that allow bidding for bundles of goods in online auctions. The emphasis of the talk will be on identifying reusable, effective scientific approaches and technologies for intelligent agent systems.