Check out the Flat Iron District. Also if there is any one thing you do in NY it is eat a pastrami on rye at Katz's Deli. And only pastrami on rye. IF you don't like pastrami then don't bother going there.

You cannot go wrong by staying in Midtown, though hotel prices are at a premium there.  Some of the providers on the board could probably give you good info on deals and rates of specific hotels.  Also the best time is during the week as a good majority of us commute in.  I try to get girls to come out to Long Island but a lot are weary.  Best idea for that would be to prebook to see if there is enough interest.  Laides typically stay in Garden City/Westbury or Melville when touring Long Island.  You may also get some interest in Westchester, CT or NJ.  Same would go as for Long Island.  See how much interest there is before booking a stay there.

If you want to see a lot of guys in Manhattan during lunch and after work, then stay in Midtown.  Midtown East is probably a better choice than Midtown West, which is code for Times Square (which sucks and no one really wants to go to).

Midtown East is very busy during the day and early evenings with lots of people working in the area, but it's not gonna be very happening at night, save for a few hot spots like Lavo and Tao, and some good restaurants.

If you want nightlife then stay towards the Meatpacking District, but bear in mind that it's not easy for guys who work on Wall Street downtown or in Midtown to get to the Meatpacking District easily during the day.

Really kinda depends on what you're looking for.