The site run by NelsonThorne, publishers of Brennpunkt, provides supplementary activities for the course which are useful for anyone working at this level. Not all the links work, unfortunately, but the grammar section is worth a visit.
The Goethe Institute also provides links on various topics relevant to the exam which are also of general interest.Practise your listening comprehension with some great videos from the Ashcombe School.
The Channel Four website offers Homework High, a service where you can ask questions about German and get an answer from a teacher. They also provide some interactive activities, at four different levels, intended to accompany the TV course Extra. It's not as useful as it might be, but has a few things worth looking at. Two stars.