Best resources for finding an apartment in Upper West Side, New York City?

Go to Craigslist and try the "no fee" or "by owner" section first under the Upper West Side section to try to avoid a broker fee. Truth be told, you probably won't be able to avoid a broker, but you never know. The vacancy in New York right now is under one percent so brokers are really ruling the roost right now and they charge 10% of a year's rent. If nothing comes up under the no fee section then try all apartments or go directly to a brokerage website to see all of their listings. Citihabitats and Bond are the two biggest in the city.