Spatial layout is frequently used for managing loosely organized information, such as desktop icons and digital ink. To help users organize this type of information efficiently, we propose an interface for manipulating spatial aggregations of objects. The aggregated objects are automatically recognized as a group, and the group structure is visualized as a two-dimensional bubble surface that surrounds the objects. Users can drag, copy, or delete a group by operating on the bubble. Furthermore, to help pick out individual objects in a dense aggregation, the system spreads the objects to avoid overlapping when requested. This paper describes the design of this interface and its implementation. We tested our technique in icon grouping and ink relocation tasks and observed improvements in user performance.