Hmmm...that's a tough one, Stephen. I'm honestly not sure if any Web site would contain sound effects of that nature. I could easily be wrong of course. I did a search on Google, and actually thought I found something, but the WAV file I found turned out to just be one of the lookouts yelling, "Iceberg right ahead!"
Also you have to look up the sound if screeching metal.
For the Titanic breaking in half, the same sound of groaning and snapping of steel structures would help. The movie had alot of that when you see Titanic sink, you an hear the hull groaning as the strain increases.