Raynox DCR250 macro adaptor if you want REAL closeups on a budget (around £30 - £40 2nd hand). The DCR250 gives around 8x magnification on a 200mm lens and fits ANY lens with filter thread > 49mm. DOF is minimal as it the focal distance (around 10cm) but you can get some awesome results:
Check out the FlickR group to see what else this lens is capable of:
http://www.flickr.com/groups/raynoxdcr250/
Regards
Carl