Flipkurl is a php-curl based api library to access the contents of flipkart.com site, login into it, search book listings, add books to cart, move books from to wishlist, read contents of cart, etc.
Usually shopping carts don't persist the user's selection across logins, but this one does. So whatever books you add via the library will stay in your account, so you can checkout/pay later from there.
Some possible uses of the API include Custom User Interfaces, Mobile UI's, Mashups with other API's, Automate stuff, etc.
The library is released under GPL. You can find the code, more details regarding the library and examples here - http://code.google.com/p/flipkurl
It was done as a fun weekend project.