We've talked before about making the most of your library card, but I wanted to touch upon my recent experiences with the New York Public Library. My wife and I had been looking for some books on investing but couldn't get them shipped to Spain cheaply. Fortunately, we still had our NYPL cards.
We've been downloading a ton of materials from the site, and I've been really impressed by the depth of their collection and the friendly user interface. The print materials are easy to access and download quickly as pdfs (I usually print them out configuring my printer to do four pages per sheet). Although the audio files Overdrive DRM is annoying, you can get the mp3s onto your iPod by first burning them to a CD through Window Media Player. You can then import the audio to iTunes.
Signing up for a membership is easy and free if you are in New York as a resident or student. You are only required to enter a name and a New York address where the card will be shipped. Afterwards you will use the card number and a pin number to access the materials. Paid memberships are also available for out-of-state or foreign users.