Today, software development is intrinsically a collaborative activity and there is still a crucial need to provide adequate computer tools well supporting collaboration in such activity. Empirical studies have already identified some requirements to provide better collaboration-aware software development environments, and theories coming from human and social sciences still help researchers to better understand these activities. Founding our work on the activity theory, we present here some important issues that have been identified for creating better software development environments. Adding our experience, we particularly emphasize an aspect of human activity that has still not really been taken into account in creating these computer supports: the user's experience crystallization and sharing. Finally, we propose an implementation supporting the identified properties in an existing and widely used software development environment