Scannav is a mapping program with all the features you'd expect from a navigation program (route definition and storage, definition of danger zones, automatic map changes, etc.). It is compatible with maptech charts (bsb format available under the marine chart link), softchart charts and the new official S57 format. Its user-friendly interface makes it easy to get to grips with.
As an option, you can add an AIS module, a tidal current module and a weather module.