This is summary sheet covering the Fuzion Athletics plyometric circuit training.
Deep push-ups are a great strength training drill, especially for the strength needed to execute the pole vaultin plant. Follow-up this link to an eHow video briefely explaining some different variations of push-ups. I particularly like the deep push-ups. I've build my own set of deep push-up bars from PVC tubes similar to the picture below.
Follow the link above to a quick video specifically showing the V Sit-up with a medicine ball. This strength drill is particularly good for developing strength for the swing and throw phase of the pole vault.