Best resources for finding an apartment in East Harlem, New York City?

Go to Craigslist for the "no fee" or "by owner" apartments if you don't want to pay a broker fee (10% of a year's rent). If you can pay a broker -- which is by far the most common and easy thing to do -- then go to the "all apartments" heading or go straight to Citihabitats or Bond's brokerage websites. A broker can get you an apartment in about 2 days but it'll cost ya.