ecfmg.org would be a good place to start.
As far as subjects go, the bulk of the questions generally come from internal medicine, pediatrics and ob/gyn. Surgery (especially trauma and orthopedics), psychiatry, public health, bioststats and epidemiology are also tested.
First Aid for Step 2 would be a good resource in learning about the test. Although it is not as good as the version for step 1 as a review source.
Hope this helps.