Appropriate educational technologies have the potential to make physics' concepts more accessible through visualization, modeling and multiple representations. Students are engaged in more powerful scientific activities and they are able to perform investigations that would not be possible without the use of technology. This paper presents examples of highly modular and flexible software products available on the internet for teaching and learning physics which were used in the classroom. They were used in different ways: first, as presentation aids for teaching a topic to the students, then to anchor and stimulate classroom discussions and finally encourage students applying and practicing new concepts and skills on their own. Experiences in grade 7 to 11 (with 13- to 17-year old students in an Austrian school) are reported. Some of the versatile tools are introduced and some suggestions for how to effectively use these interactive simulations in different learning environments are provided. In summary, simulations, hypermedia and activities with software tools were used as a follow-up to hands-on activities and empowered students to pursue their own research questions without being hindered by the limitations of "real" experiments and to construct their understanding through semi-guided exploration. (Contains 9 figures and 6 notes.)