Hybridization is a rather hot topic. You will have people that are firey on both sides of the debate. So beware of some possible backlash when talking about it.
As far as your question, normally it's within the same genius. GTP's are Morelia viridis, while Carpet Pythons are Morelia spilota, and Diamond Pythons are Morelia spilota spilota. Notice how they are all under the Morelia genius? That's generally the easier way to make crosses and hybrids.
HOWEVER... There are carpet python X ball python hybrids. And I believe Burmese X carpet hybrids. But I don't think blood X carpet has been successful.
http://www.hybridherps.com/forum/index.php?topic=24.0 here is a list. Don't know how up to date it is though.