What websites, publications or real estate professionals would you recommend to people looking for rentals in Lenox Hill, New York City?

I would start by checking Craigslist under "no fee" or "by owner" sections so you can try to avoid a broker fee (10% of a year's rent). Sadly, it is hard to avoid using a broker, though. So, if you need to find an apartment quickly, remotely, or specifically, I would call either CitiHabitats or Bond -- they're the biggest and, generally, least shady of all the broker firms.