Go to the App Store and do a search for quilting.
Robert Kaufman has a quilting calculator app.
Superior Thread has a few reference apps for threads, etc.
I save our guild's newsletter to iBooks along with patterns found on websites.
Photos is a great place to store pics taken at quilt shows, etc. I take pics with my iPhone, then email them to myself and save to Photos.
If you subscribe to any publications they will probably have an app for a virtual edition.
Have fun....I LOVE my iPad!!!