BioLogica is a site that has interactive labs and learning activities on biology that help students learn concepts. Students work through the activities, get feedback and hints and create a portfolio of their work.
BioLogica runs on Windows and Mac's. It doesn't just help students learn concepts in Biology, it also helps them make connections between different concepts and ideas. It focuses on genetics, including helping students to learn the parts, processes, and mechanisms of genetics.
The activities pose a problem for the students and then lets them solve it. The software will have the students explain their reasoning, help them with hints and eve suggest additional resources and material to help them. Teachers can monitor student performance and collect the student work into electronic portfolios.
There are also 3D interactive models of the cell on the site. These are great for helping students learn about the cell.
There are demos of the activities on the site and you can download a free copy of the prototype version of the software. http://biologica.concord.org/index.html