Calling for Free Online Data for Paediatric ECG?
I recognize this was asked like 7 months ago, but in case you're still looking for a good resource:

I used a CD of heart sounds that is called something like "Harvey Heart Sounds," which I got with the purchase of my stethoscope.  If you can find a copy of this, I found it an excellent tool when training to recognize the differences.

These are good heart sounds: http://depts.washington.edu/physdx/heart/demo.html

If you were looking for something other than the sounds themselves, then I'm not sure if you're asking about.  There are all sorts of good ECG references, especially Dale Dubin's EKG Interpretation book.  And Kablunde was the cardio textbook I used, which I liked.