Where should I sight see in New York City?

My Friend and I are going to New York from next Tues to next Sat for my brother's wedding. We can't sight see much on Fri or Sat b/c of wedding so we basically have Wed and Thurs to sight see. I've only been to New York once and only got to see Manhattan for half a day (I went to Times Square, 30 Rock, Madison Square Garden, Rucker Park, and some of Central Park) my friend's never been. So far we've decided we want to catch the Yankee game Thurs night, and the 9/11 memorial, also a ferry ride to Statue of Liberty/Ellis Island. An NBC studios tour sounds fun and I was thinking maybe rent some segways and ride through Central Park, but of course you can't (stupid bicycle unions :P) Oh and Wednesday we both have an audition at Who wants to be a Millionaire, but what else should we set out to do? also can you get tickets to Conan and Letterman just by waiting in line outside or do you need to write ahead of time. Thanks!