1. A computer system including: memory for storage of program instructions, and a processor programmed to: execute application programs, and produce a user interface, comprising: means for opening multiple instances of application programs under user control, a taskbar having indicators of application groupings, the indicators of the application groupings representing respective collections of open application program instances, and means for organizing the instances of the application programs indicated at the application groupings under user control, wherein the means for organizing responds to an operation that selects an indicator of an application instance from a grouping and moves it to the taskbar by creating a new application grouping and assigning the selected application instance to the new application grouping.