Societies:

- ACC
- AHA
- ASE
- AMA
- AOA
- TMA
- TOMA
- More...

Journals:

- NEJM
- BMJ
- Circulation
- More...

References:

- eMedicine
- UpToDate
- HARRISON'S
- More...

Usefull Stuff:

- IMDB.com
- Wikipedia
- deviantART

ECG Bank

Marriott's Practical Electrocardiography
ECG Wave-Maven - Harvard Medical School
BMJ series on the ABC's of Electrocardiography