I'll be in New York next week and have a full morning to spend till our Broadway play begins in early afternoon. We plan on visiting the Intrepid in the morning but what to do if it rains? Don't think we'll have enough time to go uptown to museums. Any suggestions on how to spend a rainy morning in the theatre district?

Walk over to Fifth Avenue to shop or down to Macy's and shop.

Indoor places to visit near Times Square:

Grand Central Station is an amazing space. It also has a very small free NYC Transit Museum, shops, and restaurants.

The Main Branch of the NY Public Library (the one with the lions out front) is another interesting building to explore, all free. There are a few exhibit spaces inside that might have someting of interest. Be sure to see the impressive main reading room upstairs, and the periodical room murals.

Visit the lobby of the Royalton Hotel--cool design by Philippe Starck. Don't miss the I-Dream-of-Jeannie bar.

Ride the ferris wheel at the Times Square Tots R Us.

excuse me,

Toys R Us

Go to the Museum of Natural History.
You will have a good 3 hours before your play. Its on the Westside of the City and you can get a cab out front or take the subway--also out front--and be at your play in 30 minutes MAX.
You can also go to the Tussaud Wax museum which is great if you like that sort of thing and is on 42nd st. Its $$$.

Here's another recommendation for Madame Tussaud's.

Go to the Morgan library (really a small museum) on Madison & about 37th or better still the Forbes museum on lower 5th ave to see the Faberge collection. Forbes is free.