In the southern sky we are fortunate enough to have a true "drop through ring galaxy" that is much brighter than Zwicky's Cartwheel.
This is the galaxy NGC 922, which displays a partial ring that was created by a smaller galaxy passing through the middle of NGC 922
There is a new image of this galaxy at the European Hubble Space Telescope website:
http://www.spacetelescope.org/news/heic1218
Here is the image, reproduced at low resolution:
