Designers and architects regularly use piles to organise visual artifacts. Recent efforts have now made it possible for users to create piles in digital systems as well. However, there is still little understanding of how users should interact with digital piles. In this paper we investigate this issue. We first identify three tasks that must be supported by a digital pilea??navigation, reorganisation and repositioning. We then present three interaction techniquesa??called HoverDeck, DragDeck and ExpandPile that meet these requirements. The techniques allow users to easily browse the piles, and also allow them to move elements between and within piles in an ad-hoc manner. In a user study that compared the different interaction techniques, we found that ExpandPile was significantly faster than the other techniques over all tasks. There were differences, however, in individual tasks. We discuss the benefits and limitations of the different techniques and identify several situations where each of them could prove useful.