Disclaimer: I did not read all of the responses.
Nothing will beat a pure macro lens. However, Canon's Close- lenses ( 250D and 500D ) that screw on the end work pretty well. ( they will work on any brand of lens provided the filter thread is the correct diameter as well as the focal length ) They aren't cheap though. Tubes work well, and can be used for things other than high magnification as well. I would recommend the Kenko set.