The "allaboutjazz" magazine and website can be a good resource too. Most players send their gig info to it, and it's free.
Iridium is right off Times Square, it's a nice room. It's expensive but there are usually really good players there, and the food is good too.
THE place to hear music, in my (non New Yorker) opinion, is in the Village downtown. The 55 Bar, Small's, and of course the Village Vanguard usually have all the players I'm really into. Definitely see if Gretchen Parlato (singer), Lionel Loueke (guitar) or David Binney (alto) are playing at the 55 Bar if you're in that area. Seeing a set by any of these people might be life changing.