Philleh's covered the euro-horror basics well, but as alex stated Bethmann is a pretty good place to start when looking at German gore-porn...
A great place to start would be:
Angel of Death 1 & 2
Dämonenbrut
Exitus 1 & 2
K3: Prison of Hell
Rossa Venezia
Plus some others I can think of off the top of my head, which haven't been mentioned:
Emanuelle and the Last Cannibals
Fantom Kiler 1-4
Guts of a Beauty
Guts of a Virgin
Satanico Pandemonium
Plus there's plenty of WIP and Nazisploitaion films, whilst not hardcore, mix aspects of sex and violence in equal measure.
The main problem with horror-porn for me, is that it's difficult to find a balance between the sex and the violence. It's either more about the horror and violence with the sex taking a back seat, or an all out ****-fest with the horror and the story being completely sidelined.
I find Bethmann is good at balncing both aspects to create some decent flicks. Don't expect oscar-worthy cinema though.
