We present a framework for building flexible collaboration environment. The framework is based on the notion of room that represents virtual shared workspace. Users can work together with collaborative applets and objects in a room. The framework allows new applets to be added to collaboration environment. It also permits users to change the configuration of shared workspace dynamically by manipulating the applets and objects in rooms. The framework supports access-controlled collaboration environment for easy access over the Internet by users. Rooms can be used not only for synchronous collaboration but also for asynchronous collaboration by supporting persistence. For the open access over the Internet, room participants are given different roles with appropriate access rights. A prototype of the model had been implemented in Java and used by users with Java-enabled Web browser. The implemented system had been used by 95 users including 79 space scientists around the world in a scientific campaign that ran for 4 days. The usage evaluation of the campaign is also presented.